TeV Particle Astrophysics 2026

Aug 30, 2026, 1:00 PM → Sep 4, 2026, 11:30 PM Asia/Tokyo

TeV Particle Astrophysics (TeVPA) is a leading international conference focused on recent developments in astroparticle physics. The 2026 edition will be held in Tendo, Japan, bringing together researchers to present and discuss the latest findings.

🕒 Schedule

• August 30, 2026 (Afternoon):
  Pre-conference Workshop: MMA-CADO
• August 31 – September 4, 2026:
  Main Conference (TeVPA 2026)

Pre-conference Workshop

A dedicated workshop, "Multi-messenger Astrophysics through Collaboration Among Different Observatories (MMA-CADO)", will be held prior to the main program. All TeVPA participants are welcome to attend with no additional fee.

This session highlights international collaboration and recent developments in multi-messenger fields, offering excellent networking opportunities.

Explore Workshop Scope & Details →

Scientific Program

Plenary and parallel sessions will cover the following topics:

• Cosmic ray physics

• Gamma-ray & Neutrino astronomy

• Cosmology

• Dark matter searches (both direct and indirect)

• Gravitational waves

• Particle physics connections

List of Plenary Speakers

Name	Affiliation	Topic
Sylvia Biscoveanu	Princeton University	gravitational-wave astronomy
Teresa Bister	Radboud University Nijmegen	probe UHECR origin with B-field configuration
Antonella Castellina	INFN, Torino	Measurements of UHECRs and their multimessenger aspects
Shion Chen	Kyoto University	Quantum Sensor Development and Wave-like Dark Matter Detection
Motoko Fujiwara	University of Toyama	The standard WIMP and that go beyond the standard WIMP paradigm
Diego Gotz	CEA Paris-Saclay	SVOM mission, GRB and rapid follow-up of gravitational wave and neutrino
Gonzalo Herrera	Harvard University & MIT	Cosmic-ray+neutrino+Dark Matter (multimessenger modeling, observation)
Alexander Kusenko	UCLA	Primordial black holes
Bing Liu	Purple Mountain Observatory, CAS	LHASSO result oriented Galactic gamma-ray emission
Yuan Liu	National Astronomical Observatories, CAS	Multimessenger transient with X-ray
Lu Lu	University of Wisconsin-Madison	An overview of the field of neutrino astrophysics and its role in multi-messenger astrophysics
Maria Petropoulou	National & Kapodistrian University of Athens	Theoretical modeling of high-energy sources, blazar/GRB emission, AGN jets
Elena Pinetti	Flatiron Institute	Phenomenological interpretation of DM (IceCube, JWST, Fermi)
Tina Pollman	University of Amsterdam (GRAPPA)	Direct DM detection
Katherine Rawlins	University of Alaska Anchorage	Galactic CR - measurements and interpretation around knee
Fuminobu Takahashi	Tohoku University	Axion cosmology, inflation
Tomislav Terzic	University of Rijeka	VHE Gamma-ray astrophysics
John Tomsick	UC Berkeley	Mission oriented future overview of MeV astronomy
Naomi Tsuji	ICRR, The University of Tokyo	Multiwavelength campaigns targeting Galactic PeVatron candidates
Tejaswi Venumadhav	UC Santa Barbara	Gravitational wave independent of LIGO
Angela Zegarelli	Ruhr-University Bochum	multimessenger phenomenology for SNe

Sunday, August 30

Multi-messenger pre-workshop

1 Welcome Address for Workshop Attendees

A brief introduction to the multimessenger programs promoted by the Japan Society for the Promotion of Science.

Speaker: Shigeru Yoshida (International Center for Hadron Astrophysics, Chiba University)

2 The Japanese multi-messenger program in the International context

Multi-messenger astrophysics has been a transformative approach to exploring the Universe, combining information from not only photons but also cosmic rays, neutrinos, and gravitational waves to probe the most energetic phenomena in Nature. Major discoveries have opened unprecedented opportunities to study the origins of cosmic particles and the physics of extreme environments. Japan has played central roles in these developments, through theoretical, observational, and experimental efforts. In this talk, I will cover some of such developments in an international context. Furthermore, through the experience of past successes, future Japanese efforts will continue to drive advances in the multi-messenger era, to help uncover the engines of cosmic explosions, identify the sources of high-energy particles, and beyond.

Speaker: Shunsaku Horiuchi (Science Tokyo)

3 Follow-up observations of IceCube events using ZTF: Lessons Learned

The astrophysical origin of high-energy neutrinos detected by IceCube remains an open question. Explosive transients, such as supernovae and tidal disruption events, have been proposed as source candidates, but their contribution has not yet been firmly established. Identifying such transients as neutrino sources requires rapid and sensitive electromagnetic follow-up observations. However, most optical follow-up observations to date have relied on 1 m-class telescopes, whose sensitivity is often insufficient to detect transients at the expected distances (redshift z < 0.5-1.0). To overcome this issue, we focus on IceCube neutrino "multiplet" events, in which multiple neutrinos are detected from a consistent direction within a limited time window. Such events provide a valuable opportunity to search for nearby sources (z < 0.1-0.3). Using archival data from the Zwicky Transient Facility (ZTF), we performed a search for optical counterparts to an IceCube multiplet event. No convincing counterpart was identified, but the search allowed us to place stringent constraints on optical transients. I will discuss the lessons learned from this search, with particular emphasis on the importance of blind analysis, and robust estimates of background contamination and detection efficiency.

Speaker: Masaomi Tanaka (Tohoku University)

4 The Data-Driven Approach to Modeling Backgrounds in Optical Transient Searches

Optical follow-up observations for IceCube high-energy neutrinos provide valuable insights into transient neutrino sources. However, their scientific interpretation depends critically on the analysis framework. Identifying a convincing counterpart or placing meaningful constraints from a non-detection requires a quantitative understanding of background contamination and detection efficiency. In this talk, I will present a data-driven framework for modeling backgrounds in optical transient searches, using an optical counterpart search for an IceCube multiplet event as a case study. We evaluate background contamination and detection efficiency using ZTF archival data from large background regions. This allows us to define selection thresholds in advance, without looking at the optical data in the neutrino arrival direction through blind analysis. I will also discuss how a blind analysis helps reduce bias in candidate selection and improves the reliability of background estimates.

Speaker: Seiji Toshikage (Tohoku University)

5 Connecting IceCube to Rubin: Prospects of Physics Based on the Subaru Experience

IceCube has been detecting cosmic high-energy neutrinos for more than 10 years, but their sources are still unknown. Transient objects, such as peculiar supernovae and tidal disruption events are proposed as efficient neutrino emitters. To identify these transients as neutrino sources, IceCube is issuing neutrino alerts, which enable us to perform electromagnetic follow-up observations. In this talk, we present our optical follow-up observations to a well-localized neutrino event, IceCube 230724A, with Subaru/HST. We construct a dedicated analysis method adopting the blind analysis policy to identify or disfavor tidal disruption events (TDEs) as cosmic neutrino sources. No TDE is found in our follow-up data set with Subaru, but future analysis with Rubin/LSST will constrain their fractional contribution to the cosmic high-energy neutrino background.

Speaker: Shigeo Kimura (Tohoku University)

6 Follow-up observations of Gravitational Waves with the Subaru: What We Could and Could Not Achieve

The Subaru telescope is one of the most powerful telescope for the multi-messenger astronomy. It has a wide-field imager, Hyper Suprime-Cam (HSC), with a field of view of 1.77 deg2, and multi-object spectrograph, Prime Focus Spectrograph (PFS), with 2,400 fibers in 1.25 deg2. In this presentation, we introduce the follow-up observations of gravitational waves with these instruments and future prospects in the era of Rubin/LSST.

Speaker: Nozomu Tominaga (NAOJ)

7 Low-Latency Gravitational-Wave Alerts and Multimessenger Astronomy: O4 Results and Future Developments

During its fourth observing run (O4), the LIGO–Virgo–KAGRA Collaboration reported hundreds of gravitational-wave events. In this talk, I will summarize the gravitational-wave alerts issued during O4 and the multi-messenger follow-up observations they triggered. Despite extensive follow-up observations, no electromagnetic counterpart has so far been identified. I will then discuss what can nonetheless be learned from the O4 events from a multi-messenger perspective. Finally, I will present the future prospects for gravitational-wave alerts and multi-messenger astronomy in the upcoming Intermediate Run (IR1) and in O5.

Speaker: Soichiro Morisaki

3:45 PM Break

Multi-messenger pre-workshop

8 Connecting IceCube to MAXI: Constraining the Origin of Ultra-High-Energy Cosmic Rays with X-ray Observations

The purpose of this study is to investigate the association between high-energy neutrino events detected by IceCube and soft X-ray transients powered by failed or choked relativistic jets. Assuming photomeson interactions as the primary mechanism for neutrino production, such transients are promising candidates for high-energy neutrino emission. The photomeson resonance condition implies that PeV-scale cosmic rays predominantly interact with keV photons, making X-ray observations particularly relevant for identifying neutrino sources. This energy range is well covered by the Monitor of All-sky X-ray Image (MAXI) aboard the International Space Station.
In this talk, we present a multi-messenger search for associations between IceCube neutrino events and soft X-ray transients using more than 14 years of overlapping IceCube and MAXI observations. The long-term overlap between IceCube and MAXI provides a unique opportunity to test neutrino source scenarios based on photomeson interactions using soft X-ray transients as observational probes. By searching for soft X-ray transients associated with IceCube neutrino events, we explore their role as candidate high-energy neutrino sources and investigate the constraints that such observations can place on neutrino–UHECR unified source models, particularly in terms of the cosmic-ray loading factor.

Speaker: Wataru Iwakiri (Chiba University)

9 Follow-up observations of IceCube events using Einstein Probe

Since the start of operations, the IceCube Observatory has been characterizing the background flux of high-energy astrophysical neutrinos. However, only a fraction of this flux has been associated with known source populations. One of the most plausible production mechanisms for these neutrinos is photohadronic (pγ) interaction. In this scenario, the energies of PeV cosmic rays and sub-PeV neutrinos naturally point to X-ray-rich environments, such as gamma-ray bursts and tidal disruption events, as promising source candidates. We performed a follow-up search for X-ray counterparts to public IceCube Gold and Bronze neutrino alerts using approximately two years of observations from the Wide-field X-ray Telescope (WXT) aboard the Einstein Probe (EP). Thanks to its unprecedented combination of a large field of view and high sensitivity, EP/WXT enables searches for X-ray counterparts at distances beyond those accessible to previous measurements. Even in the absence of a significant counterpart detection, the observations place constraints on the fraction of cosmic-ray energy injected into the radiation field (the cosmic-ray loading factor). In this talk, we present the results of this analysis for the first time and discuss their implications for the cosmic ray origin.

Speaker: Nobuhiro Shimizu (Chiba University)

10 XRISM Meets SS 433: Revealing the Dynamics and Propagation of the Jets

SS 433 is a unique Galactic microquasar that exhibits persistent supercritical accretion and relativistic baryonic jets. It is also one of the brightest microquasars in the TeV gamma-ray band and is considered a promising PeVatron candidate. We conducted SS 433 observations with the X-Ray Imaging Spectroscopy Mission XRISM, complemented by simultaneous optical spectroscopic monitoring. The X-ray microcalorimeter Resolve onboard XRISM, which achieves an unprecedented energy resolution of ~5 eV at 6 keV with high sensitivity, enabled high-resolution time-resolved spectroscopy of SS 433. These data revealed the complex motions and spatial structures of the jets in unprecedented detail. In addition, comparison of the X-ray spectra with contemporaneous optical Halpha spectroscopy provided insight into the evolution of the jet plasma from the vicinity of the compact object to the optical emitting regions. The results suggest that the plasma is relatively uniform near the compact object, while it separates into discrete blobs as it propagates outward to the optical emitting region. The other XRISM instrument, Xtend, a wide-field CCD imager, also revealed diffuse X-ray emission between the central source and the eastern/western X-ray jets, suggesting that particle acceleration may be taking place in this region. In this presentation, we will report on the jet structure and dynamics revealed by the XRISM observations, together with the optical spectroscopy. If time permits, we will also briefly discuss whether there are systematic differences in the X-ray observational properties between microquasars with and without detected TeV gamma-ray emission, including SS 433.

Speaker: Megumi Shidatsu (Ehime University)

11 HiZ-GUNDAM : The Ultimate On-Board Mission for Multimessenger Astronomy

HiZ-GUNDAM is a proposed JAXA-led mission for the 2030s designed to explore the early Universe through observations of high-redshift gamma-ray bursts (GRBs). Rapid discovery and characterization of high-energy transient phenomena are essential for identifying electromagnetic counterparts to gravitational-wave events, hidden neutrino sources, and distant GRBs. By combining wide-field soft X-ray monitoring with prompt optical/near-infrared follow-up observations, HiZ-GUNDAM will provide a powerful platform for multimessenger astronomy while probing early star formation in the high-redshift Universe.

To achieve these goals, HiZ-GUNDAM carries the wide-field soft X-ray monitor EAGLE and the optical/near-infrared telescope MONSTER. EAGLE employs Lobster-Eye micro pore optics (MPO) coupled with pnCCD detectors to monitor 0.53 sr of the sky in the 0.4–4.0 keV band and provide arcminute-class localizations of newly discovered transients.
MONSTER performs simultaneous five-band photometric observations over the 0.5–2.5 μm range with a 30-cm aperture, enabling rapid characterization of transients and identification of high-redshift candidates.

Development activities are progressing for both mission instruments. For EAGLE, the development of the MPO system has progressed through prototype construction and X-ray beam tests, which demonstrated the required imaging performance with aligned MPO assemblies. Detector studies using a dedicated pnCCD readout system have confirmed basic X-ray detection and spectroscopic capabilities. For MONSTER, simulations and onboard processing studies are being carried out to optimize the identification of high-redshift GRB candidates and the selection of follow-up targets.
In this talk, we present an overview of the HiZ-GUNDAM mission, its scientific objectives, recent R&D progress, and roadmap toward mission realization.

Speaker: Hatune Goto (Kanazawa University)

12 Coordinating access to data and expertise in multi-messenger astrophysics with ACME

In the coming years, the coordination and accessibility of telescopes and observatories across the globe will be essential for the success of multi-messenger astrophysics research. The ACME project, funded by the European Union, aims to facilitate and improve access to multi-messenger data and services. It brings together about forty institutes across Europe, covering all domains in multi-wavelength astronomy, gravitational waves, neutrinos, and cosmic rays.

ACME provides transnational and virtual access to infrastructures, data, tools, and expertise. It also offers additional opportunities for training and guidance for researchers in the field, in other disciplines, and for citizen scientists. The presentation will cover the scope of the project and the related science cases, summarise the different actions carried out by the consortium, as well as the upcoming opportunities.

Speaker: Mathieu Lamoureux (APC)

Monday, August 31

9:15 AM Welcome and Announcement from the TeVPA2026 LOC

Plenary

13 Gravitational-wave observations and multimessenger implications

Ten years after their first direct detection, the catalog of gravitational-wave sources has grown to over 300 candidate events, including all possible combinations of merging black holes and neutron stars. New data from the fourth observing run (O4) of the LIGO-Virgo-KAGRA detectors have revealed events containing black holes at both extremes of the mass distribution, events of likely hierarchical origin, and high-SNR events that allow for increasingly precise tests of general relativity. On the population level, new features and correlations are beginning to reveal the astrophysical processes shaping compact-object binary formation and evolution. In this talk, I will review these findings and the other key astrophysical insights we have gleaned from a decade of gravitational-wave discovery. I will also discuss the prospects for future multimessenger observations based on the new population insights gleaned during O4. I will conclude by highlighting what we can look forward to as we enter the second decade of gravitational-wave astronomy.

Speaker: Sylvia Biscoveanu (Princeton University)

14 Direct dark matter detection - onward into the neutrino fog

Direct dark matter experiments attempt to find evidence of the existence of the so-far unknown particles hypothesised to make up the invisible-matter component of the universe. The main focus is on WIMP-type particles, as they remain theoretically well-motivated and the scattering of galactic WIMPs in a terrestrial detector could create an observable signal. Over the past decade, these experiments have pushed sensitivity to WIMP interactions with ordinary matter across many orders of magnitude in both particle mass and cross-section, using a diverse range of target materials and detection techniques. Tonne-scale liquid-xenon detectors currently provide the strongest sensitivity to heavy WIMPs and have, in the last few years, ruled out a large number of theoretical models, while complementary approaches extend coverage to non-standard interaction types and lighter mass particles.
As these experiments advance, they are also entering a regime in which rare neutrino interactions become observable, and might soon become the dominant background to dark matter searches, linking direct detection increasingly closely to neutrino and multi-messenger astroparticle physics. This summary will review the main detection techniques, recent progress, and future directions in the field, with emphasis on the continuing search for WIMP dark matter over a wide mass range, the complementarity of different experimental approaches, and the growing role of neutrino signals and backgrounds in shaping the next generation of experiments.

Speaker: Tina Pollmann (University of Amsterdam/Nikhef)

10:30 AM break

Plenary

15 Cosmic connections: signatures of cosmic rays in gamma ray and neutrino data

Gamma ray data from distant sources shows evidence of gamma ray
cascades initiated by cosmic rays. Furthermore, the neutrinos observed
from NGC 1068 can be explained by the effects of cosmic-ray nuclei. I will
discuss these multimessenger connections and their implications for models
of blazars, high-energy cosmic rays, and intergalactic magnetic fields.

Speaker: Alexander Kusenko (UCLA and Kavli IPMU)

16 Recent Progress in UHE Gamma-Ray Sources and Diffuse Emission Studies with LHAASO and Their Implications for Cosmic-Ray Origin

The Large High Altitude Air Shower Observatory (LHAASO) has ushered in a new era of ultra-high-energy (UHE, typically above 100 TeV) gamma-ray astronomy, providing unprecedented insights into the most powerful particle accelerators in the Milky Way. In this talk, I will review recent progress in the identification and characterization of Galactic PeVatron candidates, highlighting LHAASO’s detection of an expanding population of sources such as microquasars, supernova remnants, pulsar wind nebulae, and star-forming complexes, hat are capable of accelerating particles to hundreds of TeV or even PeV energies. I will also present recent measurements of Galactic diffuse gamma-ray emission by LHAASO, which provide constraints on cosmic-ray propagation and distribution in the Milky Way. These results have important implications for multimessenger astronomy, particularly in relation to high-energy neutrino observations and the origin of Galactic cosmic rays.

Speaker: Bing Liu (Purple Mountain Observatory, CAS)

12:00 PM Lunch

CR: CR1 : Galactic Cosmic-rays I

17 Anisotropy of Cosmic Elementary particles measured with the Alpha Magnetic Spectrometer on the ISS

Analysis of anisotropy of the arrival directions of galactic positrons, electrons and protons has been performed with the Alpha Magnetic Spectrometer on the International Space Station. This measurement allows to differentiate between point-like and diffuse sources of cosmic rays for the understanding of the origin of high energy positrons or the hardening in the proton flux. The AMS results of the dipole anisotropy are presented along with the discussion of the implications of these measurements.

Speaker: Aleksandr Stuzhin (Shandong Institute of Advanced Technology)

18 Searches for Time Variation in the TeV Cosmic-Ray Anisotropy

There is an observed anisotropy in the arrival direction distribution of cosmic rays in the TeV-PeV regime, with variations on the scale of one part in a thousand. While the origin of this anisotropy is an open question, a possible factor is cosmic-ray interactions with interstellar and heliospheric magnetic fields. These magnetic fields may change over time - for example, due to changes in solar activity throughout its 11-year solar cycle. The cosmic-ray anisotropy can reflect these time-dependent magnetic fields. In addition to these possible sources, there are several known sources of time variation in this anisotropy, such as the Compton-Getting Effect from the Earth's orbital motion as well as the cosmic-ray Sun Shadow. We present a general, model-independent method to detect time variations in the cosmic-ray anisotropy. The methodology is then validated using cosmic-ray data taken by the IceCube Neutrino Observatory from 2012 through 2023.

Speaker: Perri Zilberman (University of Wisconsin - Madison)

19 DAMPE results after the first 10 years of operation

In this talk we will cover major cosmic ray and gamma ray results of the DAMPE mission after the first 10 years of operation. We will highlight the recent discovery of a universal charge-dependent structure in all primary cosmic rays, from hydrogen to iron, appearing at 14 TV rigidity. We talk about the recent progress in cosmic ray analysis at multi-TeV frontier, measurements of individual hydrogen and helium spectra towards PeV energies, and all-particle flux measurement, particularly relevant in comparison with ground ground-based experiments. We will finalize with gamma-ray highlights, including the first independent detection of the Galactic Center Excess and Fermi bubbles.

Speaker: Andrii Tykhonov (University of Geneva)

20 First Results with the TALE infill SD Array for a PeV Cosmic-Ray Energy Spectrum Measurement

The TALE infill experiment is further low-energy extension of Telescope Array Low-energy Extension (TALE), aiming to observe cosmic rays with energies from 1 PeV to 100 PeV. The goal of this project is revealing “knee” structure in the energy spectrum. 50 surface detectors (SDs) are deployed with 100-m spacing to observe this energy region. The experiment began operation in November 2023 and has been conducting stable observations since then. In this contribution, we present the energy reconstruction method optimized for TALE infill SD array, and report on the current results of data analysis and the energy spectrum measurement.

Speaker: Haruto Matsushita (Osaka Metropolitan Univ.)

21 Measurement of the cosmic-ray energy spectrum with the TALE detector in hybrid mode

The TA Low-energy Extension (TALE) experiment extends the reach of the TA experiment on the low-energy side to below $10^{16}\,$eV. A primary objective of TALE is to study the transition from galactic to extragalactic cosmic rays. The TALE detector is a hybrid observatory composed of fluorescence telescopes and a surface detector array of scintillation counters. The surface detectors are arranged with inter-counter spacing optimized for hybrid energy spectrum measurements in the low-energy region. We analyzed data collected between November 2018 and May 2023, corresponding to 1,247 hours of operation, and in this presentation, we will show the results of the cosmic ray energy spectrum measurement using the TALE hybrid detector. This measurement will play an important role in understanding the transition from cosmic rays of galactic origin to those of extragalactic origin.

Speaker: Hitoshi Oshima (Tokyo Denki University)

22 Measuring the Cosmic-Ray Proton Spectrum with the SST-1M Stereoscopic Array

The origin of galactic cosmic rays (CRs) and the nature of their acceleration up to PeV energies remains one of the central open questions in astroparticle physics. Precise measurements of the CR proton spectrum in the multi-TeV to PeV range are essential to identify spectral features linked to acceleration and propagation processes, yet direct observations are limited to a few hundreds of TeV, and indirect ground-based measurements are subject to large uncertainties from hadronic interaction models. Recently, several experiments have revealed clear spectral structures — a softening around 10–15 TeV and indications of hardening near 100 TeV — that challenge standard models of CR transport and source populations.

Although imaging atmospheric Cherenkov telescopes (IACTs) are optimized for gamma-ray astronomy, the vastly higher flux of hadronic CRs dominates the data and is conventionally rejected as background. These events nevertheless provide a high-statistics sample ideally suited to probe the CR spectrum precisely in the multi-TeV domain covered with the IACT sensitivity. The Single-Mirror Small-Size Telescope (SST-1M) array, operating in stereoscopic mode at the Ondřejov Observatory (Czech Republic) since 2023 has accumulated more than 500 hours of high-quality stereo data.

In this contribution, we present the first preliminary measurement of the CR proton spectrum obtained with the SST-1M telescopes in the energy range 3–100 TeV. The measured spectrum shows a clear softening at approximately 13 TeV, consistent with recent direct measurements from space-borne experiments. We describe the dedicated analysis chain developed for CR event selection and energy reconstruction, and discuss the dominant systematic uncertainties, with particular emphasis on contamination by heavier nuclei. The results demonstrate the potential of small IACT telescopes to deliver competitive CR measurements, enabling complementary studies of Galactic cosmic-ray physics.

Speaker: Jakub Jurysek (FZU - Institute of Physics of Czech Academy of Sciences)

DM: DM1 : Axions and Quantum Sensors

23 Broadband Axion Dark Matter Search via Heterodyne Atom Interferometry

Ultralight \textit{axion-like particles} (ALPs) are among the most theoretically motivated dark matter candidates, yet their detection remains challenging across a wide range of masses. We present a novel \textbf{heterodyne atom interferometry scheme} that dramatically extends the sensitivity of quantum sensors to ALP dark matter, covering up to \textit{six orders of magnitude} in axion mass beyond conventional configurations.

The method exploits the coupling of the ALP field to nuclear spins, $\Delta E \propto g_{aNN}\,\nabla a \cdot \mathbf{s}$, and overcomes the fundamental limitation of standard axion searches at low frequencies: the dominance of $1/f$ noise from seismic and gravity-gradient backgrounds. By applying a rotating magnetic field that induces coherent spin precession at a tunable frequency $\Omega$, the axion-induced signal is upconverted from near-DC to a well-controlled carrier, where synchronous detection suppresses environmental noise by orders of magnitude. This shifts the accessible axion mass window from the sub-Hz regime to frequencies up to $\sim\!100$\,kHz, probing a largely unexplored region of parameter space.

We implement this scheme using \textbf{fermionic $^{87}$Sr} in a Ramsey interferometry configuration, which provides direct sensitivity to internal-state energy shifts and offers superior broadband response compared to Mach--Zehnder geometries. The sensitivity of the scheme scales with interrogation time and atom number, making it complementary to existing haloscope and spin-precession experiments such as CASPEr and ABRACADABRA in the ultralight mass range ($m_a \lesssim 10^{-10}$\,eV).

To distinguish genuine ALP signals from magnetic backgrounds, we propose a \textbf{differential double atom interferometer} configuration combined with \textbf{sidereal modulation} as a direction-sensitive discriminator. This provides a robust veto against local systematic effects and constitutes a key signature of a dark matter origin. Together, these features make atom interferometry a powerful and scalable platform for next-generation ALP searches, with a clear path toward probing axion--nucleon couplings at or below the level predicted for QCD axion models.

Speaker: Dr Paul Robert (University of Florence)

24 Enhanced Dark Matter Quantum Sensing via Geometric Phase

Dark matter remains one of the central problems in fundamental physics, and cavity-based searches are a leading method for probing ultralight candidates such as axions and dark photons. In this talk, I will present a quantum sensing protocol for coupled qubit–oscillator systems aimed at improving cavity-based dark matter detection. By combining coherent displacement and squeezing, the weak dark matter signal is encoded into an enhanced geometric phase. This increases the quantum Fisher information beyond the standard quantum limit and significantly improves sensitivity to both dark photons and axions. The method suggests a promising quantum-enhanced strategy for future cavity dark matter searches.

Speaker: Dr XIAOLIN MA (KEK QUP)

25 Status of the TESSERACT Dark Matter Experiment

The TESSERACT collaboration will search for dark matter particles below the proton mass through interactions with multiple novel, ultra-sensitive detectors. Each detector technology will use athermal phonon-sensitive Transition Edge Sensors to read out the signals deposited in the various target materials. In this talk I will present on the recent progress made toward reaching this goal. First, I will discuss the recent progress from each of these detector technologies as they prepare for underground deployment in the coming years. Then, I will showcase the achievements made towards making world-leading energy resolution TESs. I will detail new insights on the “low energy excess” background and parasitic power relevant to cryogenic detectors, highlighted by the results of TESSERACT’s first above-ground dark matter search, which yielded world-leading sensitivity to dark matter below 100 MeV/c^2. I will finish with a look towards installation at Modane Underground Laboratory in 2028.

Speaker: Michael Williams (LBNL)

26 Low-Background X-Ray Detectors for the Next Generation of Solar Axion Searches

Axions and axion-like particles (ALPs) are dark matter candidates that appear in many extensions to the Standard Model. If they exist, they would be emitted by the Sun and could be converted to X-rays in a strong magnetic field. The International Axion Observatory (IAXO) and its intermediate stage BabyIAXO are the next generation of experiments looking for these solar axions. BabyIAXO will already have a sensitivity surpassing all prior experiments and probe new ALP parameter space, with IAXO improving these limits even further. Reaching this goal requires highly efficient ultra-low background X-ray detectors. There are several detectors in development for IAXO, spanning gaseous, semiconductor and cryogenic technologies, all of which have to meet challenging requirements to reach the IAXO sensitivity goals. In this talk, I will give an introduction to IAXO and BabyIAXO, with a particular focus on detector development.

Speaker: Lucinda Schönfeld (Max Planck Institute for Nuclear Physics (MPIK))

27 Probing the Parameter Space of Axion-Like Particles Using Simulation-Based Inference

Axion-like particles (ALPs) appear in various extensions of the Standard Model and can interact with photons, leading to ALP-photon conversions in external magnetic fields. This phenomenon can introduce characteristic energy-dependent “wiggles” in gamma-ray spectra. The Cherenkov Telescope Array Observatory (CTAO) is the next-generation ground-based gamma-ray observatory, designed to provide enhanced sensitivity and energy coverage (20 GeV – 300 TeV) over current Imaging Atmospheric Cherenkov Telescopes (IACTs) and offers an excellent opportunity to study such effects.

In this work, we employ Simulation-Based Inference (SBI) to explore the parameter space of ALPs, targeting the flaring states of blazars, which are among the brightest gamma-ray sources and ideal candidates for probing ALP-induced spectral modulations. Additionally, we investigate whether this inference method can reproduce ALP exclusion limits comparable to those reported in previous studies using the classical likelihood-ratio approach. This study, therefore, provides an assessment of SBI as a tool for constraining ALP–photon interactions.

Speaker: Pooja Bhattacharjee (University of Nova Gorica)

GR: GR1 : Blazars

28 New TeV gamma-ray Discoveries from the Extreme Blazar Program of MAGIC

The MAGIC telescopes are conducting a long-term observational program aimed at discovering new extreme blazars emitting at TeV energies. These sources - also referred to as extremely high-peaked BL Lac objects (EHBLs) - belong to the most energetic subclass of blazars. They are capable of accelerating particles through complex mechanisms within highly efficient relativistic jets that are closely aligned with our line of sight. They represent unique extragalactic laboratories for exploring extreme combinations of particle energies, magnetic fields, and relativistic effects. Their synchrotron emission peaks above keV energies and is then reprocessed to very-high-energy (VHE) gamma rays, often resulting in very hard TeV spectra.
In the last years, the increasing population of extreme blazars has shown emerging spectral properties, which indicate inhomogeneity within this class of sources. Recent studies have also unveiled intriguing differences in the temporal evolution of their spectral emission. These observational evidences pose new challenges to the theoretical interpretation of their energetic emission performed through the current standard acceleration and emission models for blazars, suggesting the need for more complex theoretical frameworks.
In this contribution, we present the latest results from recent MAGIC Collaboration observing campaigns aimed to increase the extreme blazars population at VHE and explore the origin of their extreme properties. Furthermore, we will present the results of the most recent observations, discussing analogies and differences with the known sources, as well as interpretations of their non-conventional spectral emission.

Speaker: Luca Foffano (INAF)

29 The blazar sequence and its TeV extension: towards a physical interpretation

Blazars, a highly energetic subclass of jetted active galactic nuclei (AGN), exhibit a broad band spectral energy distribution (SED) characterized by two broad bumps, commonly interpreted as non-thermal emission produced by relativistic particles in the jet. Over the past decades, an anticorrelation between the peak frequencies of these components and the total SED luminosity has been identified - the so-called blazar sequence - although its physical origin remains debated.
In this work, we investigate the role of TeV-detected BL Lac objects within the blazar sequence using a physical framework based on Synchrotron Self-Compton (SSC) emission models.
Unlike the original formulation of the sequence, we binned the sources according to their synchrotron peak frequency and select representative subsets of objects within each bin. For each source, we construct a SED including only data corresponding to an average state of activity.
We explore different combinations of SSC model parameters and their statistical correlations, with the aim of comparing the physical properties of BL Lac objects across different peak-frequency classes. This approach allows us to assess whether the blazar sequence can be interpreted in terms of underlying physical parameters and to ultimately identify a set of parameters that can provide a physically motivated starting point for broadband SED modeling of gamma-ray blazars.

Speaker: Ilaria Viale (INFN Torino)

30 Different dissipation mechanisms of jet underlying variability in blazars

Blazars, among the most extreme classes of active galactic nuclei, are powered by relativistic jets whose energy dissipation mechanisms remain poorly understood. The flat radio spectrum and the core-shift effect trace the spatial distributions of magnetic fields and relativistic particles, while variability encodes dynamical information about dissipation processes. However, a unified framework connecting these observables to the underlying jet physics has been lacking. Here, we present a multi-frequency analysis of the prototypical blazar Mrk 501, incorporating core-shift measurements, spectral energy distributions (SEDs), and power spectral densities (PSDs) within a conical jet model that conserves magnetic power. Our model localizes the emission regions via core-shift data, revealing the profiles of electron density and dissipation rate along the jet. Notably, simulated PSDs at high radio frequencies ($\gtrsim 15$ GHz) deviate from observations, suggesting the presence of fewer but more energetic plasmoids in the inner jet compared to outer regions. This points to distinct dissipation mechanisms operating in the inner and outer jet. Our study establishes a novel approach to probe jet stratification, linking small-scale plasmoid dynamics to global energy transport in relativistic jets.

Speaker: Hongbin Tan (Nanjing University)

31 Study on the Emission Mechanism of a TeV Blazar “OP 313” with Multi-Wavelength Observation

Blazars, a subclass of active galactic nuclei, possess relativistic plasma jets aligned close to the line of sight of the observer and exhibit broadband emission from radio to gamma-ray energies. However, the jet launching mechanism, particle acceleration processes, and the origin of high-energy emission are still not fully understood. In this study, we focus on OP 313, a flat-spectrum radio quasar (FSRQ). OP 313 is the most distant blazar detected in very-high-energy (VHE; >100 GeV) gamma rays. It has been observed by LST-1 of the Cherenkov Telescope Array Observatory (CTAO) in December 2023, and multiple gamma-ray flares have also been detected by Fermi-LAT. These properties make it an excellent target for investigating the high-energy emission mechanisms. We conducted a long-term monitoring observation from November 2023 to July 2025 using the Kanata telescope at Higashi-Hiroshima Observatory. Photometric and polarimetric observations were performed in the optical and near-infrared bands simultaneously with the HONIR instrument mounted on the Kanata telescope. We also carried out spectral energy distribution (SED) modeling with multi-wavelength data; Fermi/LAT, Swift/XRT/UVOT, Kanata/HONIR. As a result, the observed data can be well reproduced by a two-zone leptonic model. In this presentation, we discuss the high-energy emission mechanisms based on the spectral variability revealed by the long-term observations.

Speaker: Masaki Hashizume (Hiroshima University)

MM: MM1 : High-Energy Galactic Emissions I

32 Testing a Stochastic Acceleration Model of Pulsar Wind Nebulae: High-Energy Neutrinos from the Crab Nebula

Non-thermal electromagnetic radiation up to PeV gamma-rays from pulsar wind nebulae is powered by relativistic electron-positron plasma supplied by a central pulsar. The origin of the radio-emitting particles, however, remains unresolved because of their large number compared with that expected from pair cascades in the pulsar magnetosphere. A stochastic acceleration model has been proposed in which low-energy electrons responsible for the radio emission are injected from the supernova ejecta via photoionization and subsequently accelerated by turbulence in the nebula. The observed flat radio spectra are also consistent with this stochastic acceleration scenario. In this work we explore whether ions can be injected through the same process and accelerated together with the radio-emitting electrons. The accelerated ions produce high-energy neutrinos through hadronic interactions. We estimate the resulting neutrino spectra and discuss their detectability with next-generation neutrino telescopes, focusing on the Crab Nebula.

Speaker: Shuta Tanaka (Aoyama Gakuin University)

33 On Intrabinary Shocks in Spider Pulsars with Striped Winds

Spider pulsars are compact binary systems consisting of a millisecond pulsar and a low-mass companion. The relativistic pulsar wind interacts with the companion outflow, forming an intrabinary shock (IBS) associated with particle acceleration and orbitally modulated X-ray emission. These systems may also contribute to high-energy cosmic-ray positrons and are thought to harbor some of the most massive neutron stars, making them useful laboratories for studying the neutron star equation of state and evolutionary pathways. The small orbital separation places these systems in a regime where the striped pulsar wind may not have fully dissipated when reaching the IBS. While the presence of an IBS is well established, its detailed geometry, location, and physical properties remain uncertain. We investigate the interaction between a magnetized striped pulsar wind and the companion outflow using global relativistic magnetohydrodynamic simulations.

Speaker: Sebastiaan Selvi

34 Unveiling Multimessenger Emission from Hidden Cores of Microquasars

Microquasars are radio-emitting X-ray binaries accompanied by relativistic jets. They are established sources of 100~TeV gamma rays and are considered promising candidates for cosmic-ray acceleration. Motivated by recent detections of $\sim 100~$TeV photons from Cygnus~X-1 and $\sim~$PeV photons from Cygnus~X-3 by the Large High Altitude Air Shower Observatory (LHAASO), we employ the Astrophysical Multimessenger Emission Simulator (AMES) to model their multimessenger emission considering compact outflow regions as cosmic-ray accelerators, spanning from radio to ultra-high-energy gamma rays. Our results show that the observed $>$TeV gamma rays can originate from either $p\gamma$ or $pp$ interactions, depending on the location and physical conditions of the emission region, while also reproducing the lower-energy spectra. In particular, we find that explaining the PeV emission from Cygnus~X-3 requires a magnetic field of order $\sim 10^2~\mathrm{G}$ in the AU-scale blob. These different emission-region configurations yield unique, observationally testable predictions. In the $0.1-10$~TeV energy range, where current observations provide only upper limits, they predict either a deep dip, a mild suppression, or a power-law spectrum. Additionally, models involving AU-scale blob regions predict strong variability, while those invoking more extended and static external zones show more stable behavior. We also provide a possible qualitative explanation for the distinct modulation patterns across different energy bands, which relies primarily on changes in the Doppler factor and external $\gamma\gamma$ absorption. Finally, our neutrino predictions, which properly account for muon and pion cooling effects, reveal a significantly suppressed flux, indicating that detecting these sources may be more challenging than previously anticipated.

Speaker: Yujia Wei (Department of Astronomy and Astrophysics, Penn State University)

35 Multimessenger Emission from Very-High-Energy Black Hole-Jet Systems in the Milky Way

Microquasars, compact binary systems with an accreting stellar-mass black hole or neutron star, are promising candidates for high-energy particle acceleration. Recently, the LHAASO collaboration reported on the detection of >100 TeV γ-ray emission from five microquasars, suggesting that these sources are efficient particle accelerators. In microquasars, high-energy γ-rays can be produced in large-scale jets or winds. In this work, we explore the X-ray, γ-ray and neutrino emission from SS 433, V4641 Sgr and GRS 1905+105. We consider leptonic and hadronic scenarios to explain the spectra observed by LHAASO and other high-energy γ-ray detectors. We estimate the neutrino flux associated with the hadronic component and investigate the detectability of neutrinos from these sources in current and future neutrino telescopes. We find that among the three sources, V4641 Sgr has the best prospects of observation with a combined next-generation neutrino telescopes.

Speaker: Jose Carpio (University of Nevada Las Vegas)

36 The high-energy astrophysics of the Sun

The Sun is a high-energy emission source due to cosmic rays interacting with the solar atmosphere, but the physics of these emissions are still poorly understood. Fermi and HAWC solar gamma-ray observations have shown that the emission from GeV to TeV must be strongly affected by solar magnetic fields. I will discuss the progress in solar gamma-ray observations, and what they could tell us about the magnetic condition of the Sun.

Speaker: Kenny Chun Yu Ng (The Chinese University of Hong Kong)

37 High-energy multi-messenger emission from galaxy clusters

The origin of diffuse neutrinos and $\gamma-$rays is uncertain, and galaxy clusters hosting AGN and starburst galaxies are the most probable sources of these cosmic messengers. In this work, we investigate the diffuse $\gamma-$ray and neutrino emission from the Virgo, Perseus, and Coma clusters using a detailed numerical method, combining MHD simulations with Monte Carlo methods. The MHD simulation provides the distributions of temperature, gas, and magnetic field in clusters. The Monte Carlo simulations are used to investigate the cosmic-ray (CR) propagation in ICM and subsequently the secondaries stemming from CRs. Our primary assumption is that CR injection follows the gas density of clusters, providing a physically motivated approximation. High-density regions in clusters are associated with strong turbulence and prominent shock structures, making them the natural sites for efficient CR acceleration. Our predicted $\gamma-$ray flux from the individual clusters lies well below the present upper limits of LHAASO.
The MAGIC observations of the central source NGC$1275$ of the Perseus cluster are significantly higher than our results. Further, we estimated the cumulative $\gamma$-ray and neutrino fluxes from clusters with masses $\gtrsim 5\times 10^{13}\, M_{\odot}$ in the local Universe within $500$Mpc. The diffuse $\gamma-$ray flux reported by the Fermi-LAT collaboration is significantly higher than our results. Our predictions are consistent with IceCube’s existing upper limits on the unresolved neutrino flux from galaxy clusters.

Speaker: Saqib Hussain (University of Nova Gorica, Slovenia)

NU: NU1 : Application of Neutrino Measurements

38 Global Comparison of Atmospheric Muon and Neutrino Flux Measurements with MCEq Predictions

The measurement of the high-energy atmospheric muon and neutrino fluxes serves as both a fundamental probe of hadronic interaction models and the primary background for astrophysical neutrino searches. Over the last decades, experiments including IceCube, ANTARES, Kamiokande, Fréjus, and KM3NeT have provided a wealth of data across different detector media, energy ranges, and zenith angles. However, a consistent global comparison of these results is often hindered by differing experimental conditions and analysis assumptions.

In this work the different measurements have been compared to theoretical predictions computed with MCEq (Matrix Cascade Equations), a numerical tool for solving the cascade equations. A range of hadronic interaction models and primary cosmic-ray models are considered, including SIBYLL-2.3C, QGS-JET-II-04, DPMJet-III-30.6, and EPOS-LHC in combination with H3a, and H4a, GSF, GST3, and GST4. By statistically fitting the global dataset to these model combinations, the level of agreement of $ν_{μ}$, $ν_e$, and $μ$ fluxes with current atmospheric modeling benchmarks is evaluated.

In addition, the impact of varying the normalization of the prompt component of the flux is investigated, allowing its contribution to be assessed within current experimental uncertainties. This study provides a systematic cross-experiment comparison of atmospheric lepton flux measurements and offers insight into the robustness of current hadronic interaction and cosmic-ray models, highlighting both their consistency and the remaining sources of uncertainty.

Speaker: Lene van Rootselaar (TU Dortmund)

39 Earth Tomography with Atmospheric Neutrino Absorption at TRIDENT

Large-volume neutrino telescopes designed for TeV neutrino astronomy can probe the Earth’s interior through the absorption of atmospheric neutrinos traversing the planet. This provides an independent constraint on the Earth’s radial density profile, complementing conventional methods based on seismic velocity measurements. Such measurements can serve as a cross check of traditional geophysical results and thereby contribute to our understanding of the Earth’s internal structure and long-term evolution. The TRopIcal DEep-sea Neutrino Telescope (TRIDENT), a next-generation neutrino observatory in the South China Sea, is well suited for Earth tomography with high-energy atmospheric neutrinos given its 10-cubic-kilometers physical volume and excellent angular reconstruction resolution. In this work, we present a study of TRIDENT’s Earth tomography sensitivity by simulating atmospheric neutrinos in the 1–100 TeV range. We reconstruct the posterior distributions of a five-layer radial density model and derive constraints on the Earth’s large-scale density structure and related global properties, such as its total mass. We also evaluate the expected sensitivity of TRIDENT and discuss the prospects for improving neutrino-based measurements of the deep Earth.

Speaker: Jingtao Huang

40 Potential to detect prompt atmospheric neutrinos with TRIDENT

High energy neutrinos and muons produced in the atmospher are dominant backgrounds in astrophysical neutrino detection. Atmospheric neutrinos consist of a conventional component from long-lived meson decays and a prompt component from short-lived charmed hadron decays, where the latter dominates at high energies compared to the conventional component. This prompt flux, which has not yet been definitively measured, is a key uncertainty for both background modeling and the development of hadronic interaction models. This work presents the simulation of the prompt and conventional atmospheric components detectable in TRIDENT, a proposed multi-cubic-kilometer next-generation neutrino telescope in the South China Sea. The simulation provides a spectrum prediction using the CORSIKA 8 framework, with Pythia8 for hadronic interactions to include advanced interaction models and a better description of the production and decay dynamics for charmed and heavier hadrons. The spectrum demonstrates the prospect of directly measuring the prompt atmospheric neutrinos with TRIDENT.

Speaker: Yue Feng (Tsung-Dao Lee Institute)

41 Filling the Energy Gap: Measurement of the DIS Neutrino Cross Section Using 10 Years of IceCube Data

We report the measurement of the neutrino deep-inelastic scattering cross section using 10 years of IceCube data. At neutrino energies above several hundred GeV experimental constraints remain limited, with measurements from FASER extending to a few TeV and previous IceCube results probing energies above 6.3 TeV, leaving these regimes experimentally disconnected. This analysis extends sensitivity to lower energies while improving constraints at the highest energies, establishing a continuous experimental connection between accelerator-based and atmospheric or astrophysical neutrino measurements. By combining statistically independent track-like and shower-like event selections, sensitivity is achieved in the few-TeV range overlapping with FASER, alongside significantly improved precision at multi-TeV to PeV energies. The measurement spans the regime in which deep-inelastic scattering dominates neutrino interactions and provides a key input for modelling high-energy neutrino propagation and detection. These results are among the most precise determination to date in this energy range and unify previously disconnected experimental regimes.

Speaker: Colton Hill (TU Munich)

42 Visible inelasticity as a probe of tau flavor content of astrophysical neutrinos

We present a previously-unexplored approach to probing the tau component of the diffuse astrophysical neutrino flux at neutrino telescopes using the visible inelasticity of starting-track events. Tracks from muonic tau decays are biased toward higher inelasticity than those from muon neutrino interactions, providing a statistical handle to separate the two flavors. Using realistic IceCube exposures, we show that this method achieves competitive sensitivity to the tau-to-muon flavor ratio $R_{\tau\mu}$, using just a single event topology. This technique complements existing searches and introduces a powerful probe of neutrino mixing and flavor-dependent BSM effects over cosmological distances.

Speaker: Alex Wen (Harvard University)

43 Prospects of Measuring the Flavor Composition in Tau Air Shower Neutrino Telescopes with the Glashow Resonance

The flavor composition of high-energy neutrinos carries important information about their birth, propagation, and detection. The Glashow resonant interaction $\bar{\nu}_e + e^-\to W^-$ provides a powerful method to differentiate neutrinos and antineutrinos, which expands the potential of flavor composition studies. Proposed tau air shower neutrino telescopes aim to detect earth-skimming and mountain-skimming tau neutrinos above PeV. Given the decay channel $W^-\to \bar{\nu}_\tau+\tau^-$, such experiments would also be sensitive to $\bar{\nu}_e$ via the Glashow resonant interaction, thus providing a measurement of the $\bar{\nu}_e$ and $\nu_\tau+\bar{\nu}_\tau$ ratios. In this talk, I will discuss the prospects of measuring the flavor ratio and project the sensitivity of the proposed telescopes.

Speaker: Qinrui Liu (Simon Fraser University)

3:30 PM break

BSM: BSM1 : Dark Sector and Astroparticle Probes

44 Calculation of scalar condensation decay in two different approaches

The decay of a scalar condensate is an important phenomenon in cosmology, including inflation and reheating.
We compute the decay of a scalar condensate using two distinct methods: (1) an approach based on the parametric resonance of the mode functions of the daughter particles, and (2) an approach based on the effective action given by the sum of Feynman diagrams. We then demonstrate that, at lower order in a double expansion in the amplitude of coherent oscillations and the velocity of the daughter particles, the results obtained from these two approaches are equivalent.
Finally, we discuss the time evolution of the scalar-condensate decay in both frameworks.

Speaker: Kodai Sakurai

45 Thermal effects on Dark Matter production during cosmic reheating

The relic abundance of Dark Matter (DM) produced via thermal freeze-in is sensitive to the thermal history during and after cosmic reheating. In minimal models, this opens up the possibility to make predictions for collider observables by combining the requirement to match the DM relic abundance with observations of the Cosmic Microwave Background (CMB). We assess the impact of thermal corrections to the rate of cosmic reheating and the rate of thermal DM production on CMB observables and the relic abundance. We find that such corrections are generally small in the regime where they can be computed by means of finite-temperature field theory. We construct counter-examples where this general rule is violated.
Talk based on arXiv:2604.16085.

Speaker: Yannis Georis (Kavli IPMU)

46 Verifying the failing supernova constraint on dark photons with two-dimensional hydrodynamic simulations

Recent studies on the dark photon (DP) production in collapsing stars argue that the cooling effect induced by DPs can hinder supernova explosions and lead to a “failing supernova” constraint on the photon-DP mixing parameter 𝜀. In order to verify the idea, we perform two-dimensional neutrino-radiation hydrodynamic simulations coupled with the DP production with the masses of 0.3 and 0.45 MeV. We find that the shock revival does not happen until the end of the simulations when 𝜀 ≳3 ×10^{−9}. The photon-DP mixing parameter above this value can be excluded by the failing supernova argument. Interestingly, our constraint roughly coincides with the one reported by the previous studies which adopted the postprocessing framework. This result motivates one to investigate a wider parameter range of DPs with self-consistent simulations and evaluate uncertainties in the constraint.

Speaker: Kanji Mori (Keio University)

47 Gamma-ray constraints on mixed PBH-WIMPs scenario

Primordial black holes (PBHs) are compelling candidates for dark matter (DM), although current observations strongly limit their ability to account for the total DM abundance. In scenarios where the remaining DM consists of weakly interacting massive particles (WIMPs), the latter are expected to accumulate around PBHs, forming dense dark matter spikes whose properties can be predicted rather accurately. These spikes can significantly enhance the overall WIMP annihilation rate. Using observations of the isotropic $\gamma$-ray background and point-like sources in the Galactic halo, we derive new constraints on this scenario, which differ from (and are more reliable than) past extrapolations of limits on decaying dark matter. Assuming standard WIMP properties, the DM fraction in the form of PBHs is constrained to $f_\mathrm{BH} < 10^{-8}$, even for asteroid-mass PBHs. Conversely, the observation of sub-solar mass PBHs like those hinted by recent analyses of the HSC data would imply extremely strong limits on the s-wave annihilation cross section. These results highlight the strong complementarity between PBH searches and indirect detection of particle dark matter.

Speaker: Théo Paré (Montpellier Univ. LUPM)

48 Planck-Scale Constraints on Neutrino Decoherence from IceCube

Quantum gravity theories often predict spacetime fluctuations at the Planck scale, which could induce observable quantum decoherence effects. Neutrinos provide a uniquely sensitive probe of such phenomena: because they interact only via the weak force and gravity, they can maintain quantum coherence over astrophysical distances. In this talk, I will present a search for quantum decoherence using 10.7 years of neutrino data collected by the IceCube Neutrino Observatory. By examining the persistence of neutrino coherence across large baselines, we test models of quantum-gravity-induced decoherence with energy-dependent scaling. Our results significantly strengthen existing constraints and exclude minimal Planck-suppressed decoherence scenarios across a broad range of energy scalings. These findings place some of the most stringent limits to date on quantum gravity–induced decoherence and highlight the power of neutrino observatories as probes of fundamental physics.

Speaker: Tanvi Krishnan (Harvard University)

49 Search for Unmodeled Rare Events with the IceCube Neutrino Observatory

The Standard Model (SM) of particle physics is an extremely successful theory, and in many areas, it agrees to extremely high precision with experimental measurements; however, several shortcomings—such as the lack of a feasible dark matter candidate or the existence of non-zero neutrino masses—fuel belief that it is not the final theory of Nature. Despite the decades-long experimental and theoretical effort, the nature of this final theory remains elusive. One of the challenges to this effort is the breadth of signatures that new physics might produce, which would require many searches. In the contribution, I will present a machine-learning-based model-agnostic search for rare events in data from the IceCube Neutrino Observatory. This search looks for events that deviate from the expected background distribution without specifying the underlying physics model.

Speaker: Jeffrey Lazar (Université Catholique de Louvain)

50 Constraining BNS Models with sGRB Data and Forecasting Next-Generation Synergies

The landmark multi-messenger observations of the binary neutron star (BNS) merger GW170817 provided firm evidence that such mergers can produce short gamma-ray bursts (sGRBs). However, the scarcity of BNS detections in recent gravitational-wave (GW) observing runs raises a critical question: are BNS merger rates high enough to account for the full population of observed sGRBs?
We address this question by analyzing 64 BNS population synthesis models against 16 years of Fermi-GBM data. By simulating synthetic sGRB catalogs under various jet scenarios, including GW170817-calibrated structured jets and non-universal geometries, we constrain physically viable BNS properties. We demonstrate that population models predicting low local BNS merger rates ($R_{\text{BNS}}(0) \lesssim 50 \,\text{Gpc}^{-3}\,\text{yr}^{-1}$) fail to reproduce the observed sGRB population. Reconciling these low-rate models requires either non-physical jet launching efficiencies or unrealistically wide jet opening angles ($\theta_c \gtrsim 15^\circ$) that contradict afterglow constraints. We find that models with local rates of $\approx 100 \,\text{Gpc}^{-3}\,\text{yr}^{-1}$ successfully reconcile sGRB observations with realistic jet physics.
Within these constraints, we leverage our framework to forecast multi-messenger opportunities of the coming decades. Using our physics-informed BNS catalogues, we will show specific event rate predictions in the MeV and afterglow regimes for upcoming missions (THESEUS, Crystal Eye, GRINTA). We will discuss the joint detection capabilities of these electromagnetic facilities when paired with the Advanced LIGO, Cosmic Explorer, and Einstein Telescope GW networks.
Ultimately, in this talk we will highlight how an end-to-end interface between theoretical population modeling and observational strategies enables consistent, physics-informed multi-messenger predictions for future facilities.

Speaker: Alessio Ludovico De Santis (GSSI)

DM: DM2 : Major Direct Detection Experiments

51 Overview of PandaX experiment

Located in China Jinping Underground, the PandaX (Particle and Astrophysical Xenon) project consists of a series of liquid-xenon-based rare event detection experiments, aimed to search for dark matter particles and to study the fundamental properties of neutrinos. The current experiment, PandaX-4T, employes a dual-phase time projection chamber containing 3.7 tonnes of liquid xenon in the sensitive volume. In this talk, I will present an overview of the recent results of PandaX-4T and the progress of next multi-ten-tonne liquid xenon general-purpose observatory, PandaX-xT.

Speaker: Yong Yang (Shanghai Jiao Tong University)

52 Status of Solar B8 CE𝜈NS and Light Dark Matter Search in PandaX-4T

PandaX-4T is a multi-tonne liquid-xenon experiment searching for rare low-energy interactions, operating with a 3.7-tonne active target at the China Jinping Underground Laboratory (2400 m.w.e. overburden). In 2024, PandaX-4T reported the first indication of coherent elastic neutrino–nucleus scattering (CE𝜈NS) from solar B8 neutrinos using combined Run1 and Run2 data, with a significance of 2.64𝜎. This talk will summarize the analysis that led to that result and will present the current status of the CE𝜈NS search using newly accumulated Run2 exposure. In addition, the search of light dark matter signals in the same low-energy region will be presented as well.

Speaker: Qing Lin (University of Science and Technology of China)

53 Recent Results on Solar Neutrinos and Light Dark Matter searches with the LUX-ZEPLIN Experiment

LUX-ZEPLIN (LZ) is a direct dark matter detection experiment employing a 7 tonne active volume dual-phase xenon time projection chamber, located nearly a mile underground at the Sanford Underground Research Facility in South Dakota, USA. I will discuss the experiment's status and present recent results from searches for dark matter and coherent elastic neutrino-nucleus scattering (CE$\nu$NS) from $^{8}$B solar neutrinos. These results include the first $>3\sigma$ evidence of CE$\nu$NS from a cosmic source and world-leading constraints on dark matter–nucleon scattering cross-sections for WIMP masses above $5~\text{GeV}/c^{2}$. I will discuss the implications of these measurements and future prospects for the experiment.

Speaker: Daniel Kodroff (Lawrence Berkeley National Lab)

54 The PICO Dark Matter Search

The PICO Collaboration searches for Weakly Interacting Massive Particles (WIMPs) using bubble chamber technology. Filled with superheated C$_3$F$_8$, PICO detectors achieve world-leading sensitivity to spin-dependent WIMP–proton interactions through unpaired protons in the fluorine nuclei while being insensitive to gammas from electron recoils. Housed in SNOLAB in Sudbury, Ontario, Canada, the PICO-40L detector is the first large-scale implementation of the "right-side-up" bubble chamber design, in which the absence of a buffer fluid in contact with the C3F8 minimises background rates from particulates entering the chamber. PICO-40L is currently fully assembled, with some preliminary data taken, and is being recommissioned for more data collection. PICO-500 is the next-generation PICO bubble chamber. Planned to hold 260 L of C$_3$F$_8$, with a projected ton-year exposure, it will further extend PICO's sensitivity to spin-dependent dark matter detection. It is currently being assembled at SNOLAB, with major assembly milestones recently passed. This talk will present the status of the PICO-40L detector and will give an update on the assembly progress and commissioning plans of PICO-500.

Speaker: William Woodley (University of Alberta)

55 Recent results from the DEAP-3600 dark matter search experiment

The DEAP-3600 experiment is a direct dark matter search located 2 km underground at SNOLAB, Canada. It employs a spherical acrylic vessel capable of holding 3600 kg of liquid argon (LAr) target surrounded by a water Cherenkov veto system. Recent analyses has produced an updated exclusion limit on WIMP dark matter search using a Profile Likelihood Ratio (PLR) method. In addition, the DEAP-3600 experiment is sensitive to solar neutrino signals, achieving the first measurement of solar neutrino interactions in LAr. A measurement of the cosmic-ray muon flux is performed at the DEAP-3600 site using events identified in the water tank along with the coincidence signals between the water tank and inner LAr detector. Following recent hardware upgrades, the experiment is set to commence its fourth phase of data collection.

Speaker: Akhil Hitesh Maru (Carleton University)

56 The SABRE South Experiment at the Stawell Underground Physics Laboratory

SABRE is an international collaboration that will operate similar particle detectors in the Northern (SABRE North) and Southern Hemispheres (SABRE South). This innovative approach aims to distinguish potential dark matter signals from seasonal backgrounds: a pioneering strategy only feasible with a Southern Hemisphere experiment. SABRE South is located at the Stawell Underground Physics Laboratory (SUPL), in regional Victoria, Australia. SUPL is a newly constructed facility situated 1024 metres underground (∼2900 metres water equivalent) within the Stawell Gold Mine. Its construction was completed in 2023.

SABRE South employs ultra-high purity NaI(Tl) crystals immersed in a linear alkyl benzene (LAB)-based liquid scintillator veto, surrounded by passive steel and polyethylene shielding, and topped with a plastic scintillator muon veto. Significant progress has been made in the procurement, testing, and preparation of equipment for the installation of SABRE South. The assembly of the experiment at SUPL will take place this year. The SABRE South muon detector and data acquisition systems are already operational and actively collecting data at SUPL, and full commissioning of SABRE South is planned this year. This presentation will provide an update on the overall progress of the SABRE South construction, its anticipated performance, and its potential physics reach.

Speaker: Robert James (The University of Melbourne)

GR: GR2 : Galactic

57 Hadronic Scenario for Galactic PeVatron LHAASO J1912+1014u Supported by Fermi-LAT gamma-ray Data and FUGIN CO Data

LHAASO has reported 43 sub-PeV gamma-ray sources, which are promising candidates for cosmic-ray (CR) accelerators above the PeV energy, commonly called as PeVatrons. Multi-wavelength observations are crucial for identifying the underlying particle species and estimating the CR energy content of these sources. In this work we investigate the region around LHAASO J1912+1014u (and HESS J1912+101) using Fermi-LAT gamma-ray data and FUGIN CO data. We analyzed 15 years of Fermi-LAT data in the 0.4–409.6 GeV energy range. By improving the standard Fermi-LAT diffuse emission model, we significantly reduced the large residuals around the source in the 1.6-12.8 GeV band. We detected a statistically significant excess above the diffuse background, which likely represents >=10 GeV emission associated with the LHAASO/H.E.S.S. source. The GeV excess exhibits a hard spectrum (photon index of about 2.1) and is well reproduced by interstellar gas templates with systemic velocities of about 25 km/s or 60 km/s. We performed a comprehensive fit to the GeV-TeV spectral energy distribution. Although a leptonic scenario can reproduce the observed spectrum, a hadronic scenario is favored once electron cooling is considered. The inferred CR proton spectrum has an index of about 2.2, and the total CR proton energy above 1 GeV is (1–5) x 10^49 erg, depending on the assumed velocity range of the associated interstellar gas. A stringent upper limit on diffuse X-ray emission further supports the proton PeVatron scenario.

Speaker: Tsunefumi Mizuno (Hiroshima University)

58 Search for Molecular Clouds in the Dark Ultra-High-Energy Gamma-Ray Source 1LHAASO J0007+5659u with the Nobeyama 45-m Radio Telescope

The origin of Galactic sources capable of accelerating cosmic rays up to PeV energies (PeVatrons) remains a central question in high-energy astrophysics. Recently, LHAASO has detected ultra-high-energy ($E > 100$ TeV) gamma rays from approximately 50 sources, pinpointing locations of PeVatron candidates; however, about half of them remain unidentified due to the lack of observations at other wavelengths. In this study, we focus on 1LHAASO J0007+5659u, one of the dark gamma-ray sources detected only by LHAASO/KM2A. Using the Nobeyama 45-m radio telescope, we conducted $^{12}$CO, $^{13}$CO, and C$^{18}$O ($J=1\text{–}0$) observations over an area of $0.5^\circ \times 0.5^\circ$ centered on the source. We identified three molecular cloud. One of which is located near the center of the gamma-ray emission. These clouds are detected at $-38$ to $-35$ km s$^{-1}$ and $-4.2$ to $-2.3$ km s$^{-1}$. Their physical properties are estimated as follows: distances of $\sim0.4$ or $\sim3$ kpc, sizes of $\sim0.2$ or $\sim2$ pc, and number densities of $10^{2}$–$10^{3}$ cm$^{-3}$. These molecular clouds can serve as targets for proton–proton interactions, producing hadronic gamma rays via neutral pion decay. The total energy of cosmic-ray protons required to explain the observed gamma-ray flux is estimated to be $10^{43}$–$10^{45}$ erg.

We also performed similar observations toward 1LHAASO J1740+0948u, 1LHAASO J1959+1129u, and 1LHAASO J0216+4237u, but found no significant CO emission. In this contribution, we present these results and discuss the nature of the gamma-ray emission.

Speaker: Ryohei Kanazashi (Kanagawa University)

59 Supernova remnants and their role in shaping TeV emission from PeVatron candidates

The recent detection of ultra-high-energy (UHE; >100 TeV) γ-rays by LHAASO has advanced our understanding of galactic particle accelerators, providing strong evidence for PeV particle acceleration. While sources such as supernova remnants (SNRs), microquasars, and young massive clusters are the main PeVatron candidates, the origin of their UHE emission remains a subject of intense debate. A compelling narrative involves accelerated particles that escape from an SNR shock and interact with nearby dense molecular clouds, producing neutral pion-decay γ-rays. However, interpreting these emissions requires a sophisticated treatment of how particles are both confined at the molecular clouds and transported through the interstellar medium considering the source-cloud distance.

In this contribution, I present a two-phase simulation model centered on SNRs as the principal engines of particle acceleration. Utilizing our remnant-shock model and the transport pipeline based on the GAMERA code, I investigate two distinct scenarios: direct source-cloud interactions governed by shock-induced adiabatic compression, and indirect cloud illumination by cosmic rays escaping from earlier evolutionary stages. This framework is applied to the W51 complex and to LHAASO J0341+5258, targeting the recent UHE detection by LHAASO. Finally, I will discuss the physical requirements for spatially resolving these complex regions, which could be achieved by next-generation IACTs such as CTAO and the ASTRI Mini-Array, and the importance of the multi-messenger and multi-frequency analysis in order to finally disentangle hadronic and leptonic γ-ray emission.

Speaker: Alan Sunny (INAF-IAPS, Rome, Italy)

60 Time evolution of particle acceleration at supernova remnants and gamma-ray emission from clumps in the vicinity

Supernova remnants (SNRs) have been considered as a source of the bulk of Galactic cosmic rays (CR). Recently, some evidence of extended gamma-ray emission have been reported by e.g. LHAASO and H.E.S.S. and this emission often has a high maximum energy, suggesting the existence of particles escaping from acceleration regions of SNRs. Although some analytical works have explained based on the escaped CR, and have calculated the gamma-ray spectrum on the environment with SNR shock interacting with clumps and have shown the spectral hardening, such works have generally not included the CR propagation. Therefore, we revisit a setup similar to the conventional CR propagation calculation, which solved the time evolution of the spatial distribution and spectrum of the accelerated particles of evolving shock and the behavior of the evolution.

In this work, we developed the simulation code that calculates the time evolution of phase-space distribution function of CR spectrum by solving the one-dimensional diffusion-convection equation coupled with analytical solutions for shock dynamics. Our results show that the particle acceleration still increases even after the age of 10kyrs in our models. We also calculated $\pi^0$ gamma-ray emission at various stages of SNR evolution with/without clumps located at shock upstream, and compare them with several observed objects. The results show that the emission from clumps in the vicinity can dominate the total flux and significantly hardens the overall spectrum. To explain the observation data, the existence of clumps can play an important role.

Speaker: Dr Ryosuke Kobashi (ICRR, The University of Tokyo)

61 Deep view of the HESS J1303-631 region with Fermi-LAT: an SNR in disguise?

Initially unidentified gamma-ray source HESS J1303-631 has been believed to be an evolved Pulsar Wind Nebula (PWN) associated with the pulsar PSR J1301-6305 on account of its energy-dependent morphology that features shrinking of the emission region with energy towards the location of the pulsar. Primarily detected by H.E.S.S. above 1 TeV, it was subsequently also detected by Fermi-LAT at GeV energies, showing an extended emission to the east of the pulsar location. Radio observations of the surrounding region conducted with the Australia Telescope Compact Array (ATCA) showed no sign of radio counterparts of the PWN, but revealed a shell-like supernova remnant (SNR) candidate, G304.4-0.2, to the north-east of HESS J1303-631. A clear shell-like morphology of the SNR candidate, which we call Mavka, was recently confirmed by the ASKAP and MeerKAT surveys.

In this work, we revisit the GeV emission from the region and show that part of the emission initially associated with HESS J1303-631 may in fact be associated with the Mavka SNR. We perform a detailed morphology study that results in a significant detection of the gamma-ray emission spatially coincident with the remnant. We report on the data analysis results and implications of the SNR scenario.

Speaker: Martín Moró González (CIEMAT)

62 Isolated Black Holes as Potential PeVatrons and LHAASO unidentified sources

Recent discoveries of diffuse gamma rays and neutrinos from Galactic plane provide strong evidence of Galactic PeVatrons, but what kind of astrophysical objects are accelerating PeV cosmic rays are still unknown. In addition, LHAASO has identified mysterious "dark" sources with no clear counterparts at lower gamma-ray energies, posing a new astrophysical puzzle. In this talk, I will introduce isolated black holes wandering in molecular clouds as the sources of LHAASO dark sources and PeV cosmic rays observed on Earth. Isolated black holes in molecular clouds accretes surrounding dense gas, and magnetized accretion flows can accelerate cosmic rays up to PeV energies. These PeV cosmic rays escape from the accretion flows and interact with ambient molecular gas, producing ultrahigh-energy gamma-rays. Considering the population of isolated black holes in our Galaxy, they can energetically explain PeV cosmic-rays observed on Earth.

Speaker: Shigeo Kimura (Tohoku University)

GW: GW1 : Data Analysis and Compact Binary Populations

63 Status report and latest results from Indo-Japanese Pulsar Timing Array consortium

Pulsar Timing Arrays (PTAs) use an ensemble of highly stable millisecond pulsars to detect the nanohertz stochastic gravitational wave background (GWB), expected to arise primarily from a population of inspiralling supermassive black hole binaries. In addition to the detection of this stochastic background, PTAs can probe a wide range of astrophysical phenomena, including tests of gravity. I shall discuss the current status and present recent results from the Indo-Japanese Pulsar Timing Array (InPTA), including its Data Release 2 (DR2) and latest results related to gravitational wave searches.

Speaker: Shantanu Desai (IIT Hyderabad)

64 A Robust Approach to Evaluating Binary Black Hole Spin Populations from Gravitational-Wave Data

Parameter estimation and population inference for binary black holes from gravitational-wave data are limited by observational uncertainties. In particular, spin parameters—crucial for understanding the formation channels of binary black holes—remain more weakly constrained than other parameters, making it difficult to draw conclusive conclusions.
The large uncertainty in spin estimation makes inferred results highly sensitive to prior choices. To obtain more robust conclusions, we adopt a uniform prior on the effective spin, which is relatively well constrained by gravitational-wave data. We further evaluate the occurrence probability of events under assumed population models to constrain the formation channels of binary black holes.

Speaker: Kazuya Kobayashi

65 Testing the Circular Binary Hypothesis for Massive Binary Black Hole Events Using Binary Orientations

The LIGO–Virgo–KAGRA collaboration has reported several detections of massive binary black holes with total masses exceeding 100 M⊙. In addition to their large masses, some of these systems exhibit evidence of high component spins. On the other hand, owing to the short duration of their signals, these events could alternatively be explained by other transient sources. In this study, we propose a method to test their consistency with circular binary systems by examining the distribution of binary orientations. In this talk, I will present the methodology and its application to LIGO–Virgo–KAGRA events.

Speaker: Soichiro Morisaki

66 Fast gravitational-wave parameter estimation for compact binary coalescences using efficient parameterizations and normalizing flows

Over 300 gravitational wave (GW) events have been detected by the LIGO-Virgo-KAGRA (LVK) collaboration. Most of them originate from binary black hole(BBH) coalescences, and a few are from binary neutron stars (BNS). Unlike BBH signals, GWs from BNS are long signals lasting up to a few minutes in the detector band, which makes parameter estimation computationally expensive. Even with current fast methods, parameter estimation still takes tens of minutes. This is still a bottleneck for multi-messenger astronomy, where rapid follow-up observations with electromagnetic telescopes are essential. To further accelerate parameter estimation, we are developing a new approach based on simulation-based inference (SBI) using normalizing flows, a machine learning technique that learns the posterior distribution directly from simulated data. In particular, we focus on efficient parameterizations of the GW signal to reduce parameter-space complexity and enable more accurate estimation. We will present our methods and preliminary results, including a comparison with standard Bayesian inference results.

Speaker: Kazuki Takada (ICRR/The University of Tokyo)

67 Search for Sub-Solar Mass Binary Black Holes by Gravitational Waves

I'll present methods to optimize the analysis of long-duration gravitational waves (GWs) from compact binary coalescences (CBCs) and search for sub-solar mass CBCs in LIGO data using the methods. The LIGO–Virgo–KAGRA (LVK) collaboration, operating the world’s most sensitive GW observatories, searches for CBC signals in the 0.2–1.0 solar mass range, providing leading constraints on the abundance of Primordial Black Holes (PBHs).
However, low-mass CBC signals have intrinsically long durations, which pose significant computational challenges. The sensitivity of current searches is limited by the cost of dense template banks and the memory requirements of the analysis. In addition, for very long signals, the assumption of stationary noise becomes less accurate over the signal duration, making it difficult to track noise fluctuations and leading to a loss of sensitivity. To mitigate these issues, existing analyses often adopt a higher low-frequency cutoff (e.g., 45 Hz), which reduces computational demands but sacrifices sensitivity. Our study indicates that incorporating lower-frequency data could improve PBH abundance limits by up to ~36%. This issue will become even more critical for next-generation detectors, which are expected to achieve enhanced sensitivity at low frequencies and thus observe even longer signals.
To address these challenges, I develop two complementary methods: the ratio filter and the multiband matched filtering method. The ratio filter enables efficient computation of the signal-to-noise ratio (SNR) for nearby waveforms by reusing the SNR time series of a reference waveform. Multiband matched filtering mitigates the loss of sensitivity due to non-stationary noise by dividing the waveform into multiple frequency bands, allowing the analysis to better track time-dependent noise fluctuations, while also reducing computational cost.
Using these methods, I conduct a search for sub-solar mass CBCs in LIGO data and present the result.

Speaker: Yasuhiro Murakami

68 Estimation of the fpeak Precision for Future KAGRA from Post-Merger Gravitational Waves of BNS Coalescences

In this study, we focus on the high frequency gravitational-wave emission from the hyper-massive neutron star temporarily formed after a binary neutron star (BNS) merger. We evaluate how accurately KAGRA can estimate the post-merger peak frequency $f_{\mathrm{peak}}$ using the BayesWave analysis on numerical-relativity waveform models injected into Gaussian noise colored by the detector’s PSD. Since $f_{\mathrm{peak}}$ strongly depends on the dense matter equation of state, its estimation is crucial for placing physical constraints. Using the planned future KAGRA sensitivity optimized for the high frequency band, we assess KAGRA’s potential to constrain neutron star physics for BNS signals at various distances. Our results indicate that a signal to noise ratio of approximately 6–7 in the post-merger band is required for BayesWave to reliably reconstruct $f_{\mathrm{peak}}$ for EOS discrimination.

Speaker: Yuto Ichinose (U.Tokyo ICRR)

69 A Joint Search for the Electromagnetic Counterpart to the Gravitational Wave Binary Black Hole Merger Candidate S250328ae with DECam and PFS

We present results of a joint search with the Dark Energy Camera (DECam) and Prime Focus Spectrograph (PFS) for the optical counterpart of the LIGO-Virgo-KAGRA event S250328ae, a binary black hole merger candidate of high significance detected at a distance of 511+-82 Mpc and localized within an area of 3 (15) square degrees at 50% (90%) confidence. We observed the 90% confidence area with DECam and identified 36 high-confidence transient candidates after image processing, candidate selection, and candidate vetting. We observed with PFS to obtain optical spectra of DECam candidates, Swift-XRT candidates, and potential host galaxies of S250328ae. In total, 3897 targets were observed by seven pointings covering ~50% of the 90% confidence area. After template fitting and visual inspection, we identified 12 SNe, 159 QSOs, 2975 galaxies, and 131 stars. With the joint observations of DECam and PFS, we found variability in 12 SNe, 139 QSOs, 37 galaxies, and 2 stars. We do not identify any confident optical counterparts, though the association is not ruled out for three variable candidates that are not observed by PFS and 6 QSO candidates without clear variability if the optical counterpart of S250328ae is faint. Despite the lack of confident optical counterparts, our study serves as a framework for future collaborations between wide-field imagers and multi-object spectrographs to maximize multi-messenger analyses.

Speaker: Haibin Zhang (NAOJ)

MM: MM2 : High-Energy Galactic Emissions II

70 High-Energy Emission Analysis from the Galactic Center Region with HAWC and IceCube

Observations by the High-Altitude Water Cherenkov (HAWC) Observatory have revealed gamma-ray emission from the Galactic Center (GC) region extending beyond 100 TeV with an unbroken power law, indicating the presence of a powerful particle accelerator. If this emission is of hadronic origin, a corresponding flux of high-energy neutrinos is expected. We present an update on HAWC analyses of the GC region, incorporating additional data and improved gamma–hadron separation using machine learning techniques, yielding a maximum significance of 8.5$\sigma$. The best-fit model consists of a point-like source and Galactic diffuse emission modeled with HERMES (High-Energy Radiative Messengers). Motivated by this scenario, we construct a corresponding neutrino emission template for the same region of interest, embedding a point-source component while preserving the spectral index and flux ratio measured by HAWC. Using 12 years of IceCube’s point-source dataset, we perform a likelihood analysis based on this spatial template and present results on the normalization of the neutrino flux.

Speaker: Sohyoun Yun Carcamo (Drexel University)

71 Characterising the Galactic Neutrino Emission with IceCube

The Galactic Plane has been established as a source of high-energy neutrino emission with a significance beyond 5 sigma using Galactic diffuse neutrino emission models. We discuss the results of a model-independent measurement of the Galactic emission with 10 years of IceCube cascade data, which provides confidence intervals on the neutrino flux and the spectral index in different regions of the Galactic Plane at TeV energies.

For the inner Galactic region $|l|<30^{\circ}, |b| < 8^{\circ}$, the average per-flavor neutrino flux $E_{\nu}^2\Phi_{\nu+\bar\nu}$ at $E_\nu=5\,\mathrm{TeV}$ in units of $10^{-11}\,\mathrm{TeV\,m^{-2}\,s^{-1}\,sr^{-1}}$ is measured to be $21.4^{+6.3}_{-5.2}$ while for the outer Galactic Plane $|l|>60^{\circ}, |b| < 8^{\circ}$ it is measured to be $4.3^{+2.6}_{-2.4}$. The spectral index fit in the inner and outer region is $\gamma = 2.76^{+0.17}_{-0.15}$ and $\gamma = 3.10^{+0.40}_{-0.39}$, respectively.

For the first time, a direct comparison between the neutrino measurement and TeV gamma-ray emission reported by LHAASO is performed in the same region of the Galactic Plane. This is made possible by the model-independent nature of this measurement, which provides flux estimates in specific regions rather than relying on full-sky spatial templates. The results of this analysis, combined with improved data samples from IceCube and new data from KM3NeT, demonstrate that it is becoming possible to test models of Galactic diffuse emission, make direct comparisons between neutrino and gamma-ray measurements, and ultimately directly constrain the hadronic fraction of gamma-ray observations in the plane of the Galaxy.

Speaker: Ludwig Neste (Stockholm University / Oscar Klein Centre)

72 Searching for Galactic PeVatrons with ICEMAN

IceCube has detected neutrinos originating from the Galactic plane at 5.7σ suggesting the possible existence of Galactic neutrino sources. Additionally, gamma-ray observatories such as HAWC, LHAASO, and H.E.S.S. have detected Galactic gamma-ray sources with photon emission exceeding 100 TeV. If produced in hadronic interactions, these gamma-ray sources hint at the existence of Galactic PeVatrons, cosmic accelerators capable of accelerating cosmic rays up to PeV energies. Detecting neutrinos in coincidence with gamma-ray sources provides smoking gun evidence for Galactic PeVatrons. In this analysis, we use the IceCubE Multi-flavor Astrophysical Neutrino (ICEMAN) dataset to search for neutrino sources. The ICEMAN dataset combines three largely independent datasets consisting of starting muon tracks, through-going muon tracks from the north, and in-ice particle showers to provide improved all-sky sensitivity. We will present an individual point source search corresponding to >100 TeV gamma-ray sources, an analysis of the Cygnus Cocoon region, and a point source search of the entire sky. Furthermore, we will discuss the prospects of differentiating the source and diffuse components of the Galactic neutrino flux.

Speaker: Leo Seen (University of Wisconsin - Madison)

73 A minimal two-population model of cosmic ray spectra at TeV-PeV energies

Latest measurements of spectra of different cosmic ray elements at TeV–PeV energies, as well as the all-particle spectrum and mean logarithmic mass, provide a wealth of new information for models of Galactic cosmic ray acceleration and propagation. At the same time, a consistent interpretation of all available datasets remains challenging, and different theoretical frameworks are often not readily distinguishable in the data. In light of this, we seek to build a minimal phenomenological model that self-consistently explains all observables in the chosen energy range as measured by the relevant experiments. The model is built on basic physical assumptions: power-law injection spectra, modified during propagation in a rigidity-dependent way. We perform a global fit to all available datasets, accounting for energy-scale uncertainties and consistency between elemental and all-particle measurements. We show conclusively that the data cannot be adequately described by a single-population model, in which all observed spectral features are attributed to propagation effects, even without including the latest LHAASO measurements of proton and helium spectra. A two-population model emerges as the next minimal alternative, featuring one population with lower maximum energy that provides the bulk of the CR energy density (SNR-like), and a second population of more energetic but rarer sources (e.g., microquasar-like). The hardening of elemental spectra around ~150 TV is produced by the interplay between the two populations. The softenings at ~13 TV and ~3 PV (the knee) are instead interpreted as genuine breaks in populations’ spectra, arising either from propagation effects or from maximum acceleration energies.

Speaker: Igor Vaiman (Gran Sasso Science Institute; INFN, Laboratori Nazionali del Gran Sasso)

74 Explaining the Measured Cosmic-Ray Nuclei Spectra with a Dual Source-category Model

Title:
Explaining the Measured Cosmic-Ray Nuclei Spectra with a Dual Source-category Model

Abstract:

Preliminary results shown by the CALET (Calorimetric Electron Telescope) collaboration at the ICRC2025 conference [P. Brogi et al. POS(ICRC2025)019] indicate a break in the proton-helium ratio in the TeV energy range. Assuming cosmic-ray acceleration and propagation mechanisms to be independent of the species, this break could indicate that two cosmic-ray source categories exist, with different helium abundance and different spectral indices and/or cut-off rigidities. These could be different stages in supernova-remnant (SNR) evolution, or SNRs of different star types, with Wolf-Rayet stars being a possible helium-rich source.
This two source-model has been implemented in the numerical cosmic-ray propagation calculation code DRAGON, and the associated input parameter space explored to find source and propagation parameters, which give the best fit to measured nuclei spectra and primary to secondary ratios.
It is shown that such a model with a common source power-law index for all nuclei, but different helium abundance for the two source components, can explain both the break in the proton-helium ratio and the harder index of the measured helium spectrum compared to that of protons and other nuclei, while within experimental uncertainty matching various spectra and ratio measurements by CALET, AMS-02 (Alpha Magnetic Spectrometer) and other experiments.
In addition to discussing this result and the implications of the found best-fit propagation conditions, the machine-learning based methods to explore the model's parameters space will be presented.

Speaker: Holger Motz (Waseda University)

75 The role of TeV-PeV cosmic rays in the Milky Way and beyond

Within the disk of the Milky Way, GeV-range cosmic rays (CRs) are known to be energetically comparable to other components in the interstellar medium, while TeV-PeV-range CRs are very minor. However, the situation should be different after such CRs have escaped the disk and propagate to the scales of the much more tenuous circumgalactic medium (CGM) and/or intergalactic medium (IGM). Depending on the CR diffusion coefficient, there will likely be regions in the CGM or IGM where GeV CRs cannot reach even within a Hubble time. We discuss the likelihood that TeV-range CRs can reach and be energetically important in the warm-hot IGM (WHIM) residing in cosmic filaments, while PeV-range CRs may do so for the cool, diffuse IGM permeating cosmic voids. Such CRs can potentially affect the rate of gas accretion onto halos and filaments and hence the cosmic star formation rate, the observability of the WHIM and/or the Ly alpha forest, and possibly measurements of some cosmological parameters. We also discuss multimessenger observational tests. As these effects depend to some extent on the nature of the CR sources, clarifying their identity can also be important for studies of galaxy evolution and cosmology.

Speaker: Susumu Inoue (Chiba University / ICRR, University of Tokyo)

76 LOFAR follow-up of sources in the First LHAASO Catalogue

The First LHAASO Catalogue of Gamma-ray Sources (1LHAASO) lists 90 sources, 43 of which show ultra-high-energy (UHE) emission extending beyond 100 TeV, raising pressing questions about the identity of the underlying PeVatrons. A multiwavelength characterization of these sources is essential to constrain the particle acceleration mechanisms at work. We present a systematic search for low-frequency radio counterparts to the 57 1LHAASO sources that fall within the footprint of the LOFAR Two-Meter Sky Survey (LoTSS DR-3), which covers a substantial fraction of the Galactic plane at 144 MHz with 6″ resolution.

For sources in the inner Galaxy, we combine LOFAR data with MeerKAT 1.3 GHz images from the SARAO MeerKAT Galactic Plane Survey (SMGPS) to construct spectral index maps that distinguish thermal from non-thermal emission, directly informing the SNR versus H II region nature of candidate counterparts. In the outer Galaxy, where source confusion is lower, we identify several new SNR and PWN candidates coincident with 1LHAASO sources, including a new SNR/PWN candidate (G123.4+1.0) associated with 1LHAASO J0056+6346u, located within a ~3° molecular cavity. In the inner Galaxy, we find that the majority of 1LHAASO sources in the first quadrant are coincident with known SNRs, SNR candidates, or thermal emission complexes, and we identify several new SNR candidates from the LOFAR data alone.

These results demonstrate the power of low-frequency, high-resolution radio surveys as a tool for the identification and classification of Galactic PeVatron candidates detected by LHAASO.

Speaker: Maria Arias (Instituto de Astrofisica de Andalucia - CSIC)

6:30 PM Reception

Tuesday, September 1

Plenary

77 Covariant effective field theory search results with the LUX-ZEPLIN experiment

The LUX-ZEPLIN (LZ) dark matter search experiment, a dual-phase xenon time projection chamber operating at the Sanford Underground Research Facility in Lead, South Dakota, USA, has demonstrated the world's leading sensitivity to searches for Weakly Interacting Massive Particles (WIMPs). It comprises 7 tonnes of liquid xenon as an active target viewed by photomultiplier tubes (PMTs), xenon Skin and the outer detector (OD) made of gadolinium-loaded liquid scintillator. The Skin and the OD are also instrumented with PMTs and serve as veto systems against background events from radioactivity and cosmic muons. Beyond the standard spin-independent and spin-dependent WIMP interactions, LZ's exceptional sensitivity enables a comprehensive search for dark matter through a model-agnostic non-relativistic effective field theory (NR-EFT) framework, probing covariant Lagrangians arising from vector, axial, and dipole WIMP-nucleon couplings. This talk will highlight the results of the most recent LZ NR-EFT analysis.

Speaker: Sam Eriksen (University of Bristol)

78 Multimessenger astrophysics at ultra-high energies: results from the Pierre Auger Observatory

Photons, gravitational waves, neutrinos and cosmic rays carry complementary information about individual cosmic sources and their populations, offering an exceptionally powerful tool for probing the properties of the Universe. In the extreme energy regime, above $10^{17}$ eV, the Pierre Auger Observatory plays a leading role in multimessenger astronomy, owing to its capability to discriminate extensive air showers initiated by ultra-high energy photons and neutrinos from those of hadronic origin. Searches for diffuse fluxes or point-like sources of neutrinos and photons enable the study of various candidate sources and allow limits to be placed on the emission of these neutral messengers from merger events associated with gravitational waves. Neutrinos and photons also open a window onto potential effects beyond the Standard Model of particle physics, such as the decay of super-heavy dark matter or the violation of Lorentz invariance.
An overview of the multimessenger activities conducted by the Pierre Auger Collaboration is presented, along with a discussion of the improvements expected from the upgraded Pierre Auger Observatory, AugerPrime.

Speaker: Antonella Castellina (INFN)

10:30 AM break

Plenary

79 Hunting New Physics in the Dark Universe

Dark matter provides compelling evidence for physics beyond the Standard Model, motivating a broad landscape of candidates ranging from weakly interacting massive particles to ultralight axions. Astrophysical observations offer a complementary avenue to laboratory experiments for testing dark matter models across a broad range of masses and interaction strengths.
In this talk, I will present novel observational strategies designed to uncover signatures of new physics and highlight the opportunities opened by current and next-generation observatories.

Speaker: Elena Pinetti (Flatiron Institute/Simons Foundation)

80 MeV gamma-ray astronomy and COSI

Observations in the MeV gamma-ray band provide enormous potential for obtaining fundamental results on topics ranging from nucleosynthesis via studies of nuclear emission lines to multimessenger astrophysics (MMA) through detections of gamma-ray bursts (GRBs) and other transients. Due to the challenges of operating in the MeV band (~0.1-100 MeV), it is one of the least explored regions of the electromagnetic spectrum, leaving a large potential for discovery. In order to take advantage of this scientific opportunity, there is significant activity on space missions that operate in this energy range. Coming up soon is the Compton Spectrometer and Imager (COSI), which is a NASA Small Explorer (SMEX) mission with a planned launch into low-Earth orbit in 2027. Using the Compton technique, COSI will survey the entire sky at 0.2-5 MeV. COSI provides imaging, spectroscopy, and polarimetry of astrophysical sources, and its germanium detectors provide excellent energy resolution for emission line measurements, including the positron annihilation line at 511 keV and nuclear lines. However, COSI only covers part of the "MeV gap," and concepts for covering higher energies are being developed. In this talk, I will give an update on COSI and describe the status of closing the MeV gap.

Speaker: John Tomsick (University of California, Berkeley)

12:00 PM Lunch

CR: CR2 : UHECR measurements with Radio and future observatories

81 POEMMA Balloon with Radio

Earth-skimming tau neutrinos with energies above ~10 PeV can convert to tau leptons and decay in the atmosphere, initiating upward-going extensive air showers. POEMMA Balloon with Radio (PBR) is designed to measure these showers via a novel hybrid of optical Cherenkov and low-frequency radio measurements. The ability to point the detector above and below the limb will allow the observation technique to be validated on the much more abundant cosmic ray signal. While the integrated exposure and resultant sensitivity to the diffuse neutrino flux will not be competitive with that of long-term ground-based experiments that can run for decades, the instantaneous acceptance will be comparable. This, combined with the ability to point at specific targets of opportunity, will allow PBR to set competitive limits in response to astrophysical transients. PBR will fly on a NASA super pressure balloon for as long as 50 days, with a launch planned for 2028. This contribution will describe the payload, its current status and its expected capabilities.

Speaker: George Filippatos (University of Chicago)

82 Scientific objectives and recent developments of the Global Cosmic Ray Observatory

The origin of ultra-high-energy cosmic rays (UHECRs) is one of the most intriguing mysteries in astroparticle physics and high-energy physics. With an ability to select events by the rigidity $(E/Z)$, arrival directions of UHECRs can be exploited to probe the most extremely energetic phenomena in the universe. The Global Cosmic Ray Observatory (GCOS) is a proposed next-generation observatory to elucidate these origins through precise measurements of UHECRs with unprecedented exposure and mass identification capabilities. We will share ideas and requirements for GCOS summarized in https://arxiv.org/abs/2502.05657 and report the recent advances in detector developments and future perspectives.

Speaker: Toshihiro Fujii (OMU, NITEP)

83 Geo-synchrotron X-ray emission from extensive air showers: a new detection channel for high-altitude cosmic ray and neutrino observatories

We present a comprehensive study of synchrotron X-ray and gamma-ray emission (10 keV to 1 GeV) from extensive air showers (EAS) induced by ultra-high energy cosmic rays and Earth-skimming tau neutrinos, as a novel and complementary hybrid detection channel for future high-altitude observatories.

Unlike Cherenkov or fluorescence emission, geo-synchrotron radiation is dominated by shower electrons above $\sim$ 100 GeV and peaks during early shower development (shower age s $ \lesssim $ 0.5), making it uniquely sensitive to a poorly constrained phase of shower evolution and a valuable probe of shower universality, primary composition in the PeV regime, and early shower physics. To explore this channel, we developed a dedicated simulation framework that combines analytic synchrotron emission models with parameterizations of the electron distributions in the shower. Within this framework, we compute X-ray photon fluxes at a high-altitude detection plane and derive first-order event rate estimates for simplified detector configurations, including a representative sub-orbital platform. These results provide an initial assessment of the detectability of the signal and of the key parameters driving the expected yield.

In this contribution, we present the current status of the framework and its first applications, and discuss possible optimization strategies for observation altitude and detector design. We also outline ongoing work aimed at improving the modeling of early shower development, including dedicated CORSIKA simulations of young, horizontal showers in the rarefied upper atmosphere, with the goal of validating and extending existing shower descriptions in a largely unexplored regime.

Speaker: Rodrigo Alberto Torres Saavedra (Gran Sasso Science Institute and INFN-LNGS)

84 Semi-analytical modeling of in-ice radio signals from cosmic-ray particle cascades

To detect ultra-high energy neutrinos, experiments such as the Askaryan Radio Array (ARA) and the Radio Neutrino Observatory in Greenland (RNO-G) rely on radio antennas deployed in ice to detect particle cascades. This requires characterizing the in-ice radio emission from cosmic rays, which constitutes both a calibration source and a major background in the search for neutrinos. The accurate modeling of this emission currently relies on computationally expensive Monte-Carlo simulations such as FAERIE, which prohibits efficient exploration of the full parameter space. We present a semi-analytical modeling of in-ice cosmic-ray-induced radio emission. Our method combines a dedicated library of FAERIE simulations with scaling laws that capture the dependence of the signal amplitude, polarization and frequency on shower parameters. This approach will enable fast estimates of cosmic ray emission, opening the path towards shower reconstruction and event-rate predictions for in-ice radio detectors.

Speaker: Simon Chiche (Université Libre de Bruxelles)

85 Progress Toward a Sub-Threshold Search for the Radar Echo Telescope for Cosmic Rays

The Radar Echo Telescope for Cosmic Rays (RET-CR) is a pathfinder experiment for a future neutrino telescope, using cosmic rays as an in-situ test beam as a validation of the radar echo technique. The buried radar system monitors for echoes off high-energy cosmic-ray induced in-ice cascades. This work presents progress towards a future sub-threshold analysis of the RET dataset. The RET signal and dataset are well suited to a sub-threshold search, using machine learning tools and singular value decomposition to search for low SNR signals. As a first application, we present an analysis of background data demonstrating some of our analysis techniques.

Speaker: Curtis McLennan (University of Kansas)

86 The NUSES space mission

NUSES is a space mission, equipped with two scientific payloads named, Zirè and Terzina. Zirè is a hybrid detector comprising a fiber tracker, plastic scintillator and a segmented GAGG calorimeter, designed to measure the cosmic ray composition (electron, proton and lighter nuclei) from few MeV to 300 MeV, while simultaneously detecting gamma ray transients up to 50 MeV. Terzina employs an innovative approach to study ultra-high-energy astroparticle physics from space. It is developed to detect Cherenkov radiation from air showers initiated by cosmic rays (> 100 PeV) and from Earth-skimming neutrinos. Both the payloads are equipped with a novel SiPM based readout system, testing this technology in the space environment for future space missions. This presentation will discuss the major science goals, technological advancements and current status of the mission.

Speaker: Diptiranjan Pattanaik (Gran Sasso Science Institute)

DM: DM3 : Astrophysical and Cosmological DM Probes

87 Beyond Spherical Assumptions: CTAO Sensitivity to Dark Matter in Dwarf Spheroidal Galaxies

Milky Way dwarf spheroidal galaxies (dSphs) are among the most promising targets for indirect dark matter (DM) searches. A key ingredient in robust predictions of DM annihilation signals is an accurate characterization of the DM profile in these systems.

In this work, we investigate the impact of non-spherical DM halo structures on gamma-ray observations with the Cherenkov Telescope Array Observatory (CTAO). We construct J-factor maps based on non-spherical dynamical models of dSphs and perform a full analysis incorporating CTAO instrumental response using Gammapy. We then derive projected constraints on the DM annihilation cross section.
In this presentation, we discuss the impacts of dSphs morphology on CTAO sensitivity to DM annihilation signals quantitatively, building axisymmetric density profile models based on the recent kinematical data of several targets. 
We also assess the uncertainties originates from profile parameters.

Finally, we highlight future prospects enabled by synergy with upcoming spectroscopic data from the Subaru Prime Focus Spectrograph (PFS), which will significantly improve constraints on DM profiles in dSphs.

Speaker: Kohei Hayashi (National Institute of Technology, Sendai College)

88 Search for Line-Like Gamma-Ray Signals from Dark Matter in the Galactic Center with CTAO LST-1

Very-high-energy (VHE) gamma-ray observations of the Galactic Center (GC) have placed stringent constraints on dark matter candidate models, including supersymmetric wino and higgsino scenarios, with sensitivities approaching the predictions of thermal relic models. The Large-Sized Telescopes (LSTs) of the next-generation gamma-ray facility, the Cherenkov Telescope Array Observatory (CTAO), which is scheduled to begin operation in the coming years, are expected to provide timely and critical opportunities for dark matter searches.

The first LST, LST-1, has been taking GC data since 2020 and has demonstrated its observational capability. Its field of view, about 4.5 deg in diameter, is relatively large compared with those of current-generation instruments of the same class, particularly those in the Northern Hemisphere, enhancing sensitivity to spatially extended emission. Owing to its location, LST-1 observes the GC at large zenith angles, where sensitivity at TeV energies increases by more than a factor of two, at the cost of raising the energy threshold to hundreds of GeV. The combination of these characteristics, the large field of view and the observations at large zenith angles, is currently unique and already gives LST-1 competitive reach for line-like dark matter searches, despite the limited exposure. However, these features generally lead to larger systematic uncertainties and pose analysis challenges. With the development of dedicated analysis schemes, LST-1 already enables high-sensitivity observations of TeV diffuse gamma rays across this region, even in a monoscopic configuration.

Using about 40 hours of GC data obtained with LST-1, we performed a search for VHE gamma-ray signals from dark matter annihilation, focusing on so-called monochromatic lines with the aim of identifying these narrow spectral features in the GC data. Systematic uncertainties in this analysis were evaluated using both dedicated simulations and off-source data. We found no significant line-like excess and derived upper limits on the dark matter annihilation cross section. In this contribution, we report the results of the LST-1 data analysis and discuss the prospects for the forthcoming LST array.

Speaker: Dr Shotaro Abe (Kyoto U)

89 Search for Dark Matter Annihilation in the Sun and Solar Atmospheric Neutrinos with IceCube

We present a search for neutrinos from the Sun using IceCube IC86 data, targeting two complementary physics goals. The primary objective is to constrain dark matter annihilation in the solar core, where gravitationally captured WIMPs accumulate and annihilate into Standard Model particles, producing neutrinos detectable by IceCube. The secondary objective is the detection of solar atmospheric neutrinos, produced by cosmic-ray interactions in the solar atmosphere, which serve as both an irreducible background to the dark matter search and a signal of independent interest. We introduce a novel machine-learning-based event selection and present initial sensitivities across multiple WIMP annihilation channels and mass ranges, as well as to the solar atmospheric neutrino flux.

Speaker: Felix Yu

90 Cosmology-informed constraints on the fuzzy dark matter mass from dwarf-spheroidal stellar kinematics

Fuzzy dark matter (FDM) predicts a solitonic core within halos, in contrast to the cuspy inner profiles expected in the standard cold dark matter (CDM) model.
We investigate differences in the inner structure of dark matter halos through the stellar kinematics of dwarf spheroidal galaxies, which place constraints on the FDM particle mass.
We analyze the parameter space using a statistical framework with cosmology-informed priors derived from the Semi-Analytical SubHalo Inference ModelIng (SASHIMI), which restrict the outer NFW-like halo parameters to cosmologically motivated regions.
Guided by recent FDM simulations, we further assume a smooth connection between the inner soliton and outer NFW-like profiles, enabling an efficient constraint on the FDM mass. As shown in the previous study, Segue 1 provides most stringent constraint $m_{FDM}>10^{-21}~\mathrm{eV}$ even when the cosmological priors are taken into account.

Speaker: Shunichi Horigome (Tohoku University)

91 Dark Matter Heating of Compact Stars by Particle Beams

Compact astrophysical objects, such as neutron stars and white dwarfs, can act as detectors of energetic particle fluxes originating from astrophysical accelerators. While most existing capture and heating calculations assume isotropic very low energetic incident fluxes from the halo dark matter, many realistic sources produce highly directional beams or jets, for which gravitational focusing, trajectory multiplicity, and local energy deposition must be treated consistently. In this work, we develop a general relativistic formalism to compute the local density, capture probability, and energy deposition of particles arriving as directed beams onto compact objects. The framework is based on the mapping of an asymptotic particle flux to local densities through geodesic congruences, allowing for gravitational focusing, multi-stream regions, and optical depth effects to be incorporated in a unified way. The formalism applies to arbitrary particle species and interaction models, and separates capture from through-going energy deposition in a frame-consistent manner. As an explicit application, we consider relativistic particle beams generated in astrophysical jets and evaluate their interaction with two compact objects samples: a white dwarf and a neutron star. In particular, we illustrate the framework using boosted dark matter produced in a list of 324 blazars as a representative case study, computing the resulting fluxes and the associated heating in the selected stars. Additional regimes such as the interaction roof and geometric limit are discussed, highlighting the conditions under which compact objects can efficiently convert incident beam energy into observable heating.

Speaker: Shihwen Hor (T. D. Lee Institute)

GR: GR3 : Binaries/microquasars

92 XRISM/Xtend detection of diffuse X-ray emission in the "inner cavity" region around SS433

Recent detection of very-high-energy gamma-rays exceeding 10 TeV from several microquarsars suggests that microquasars are accelerating particles with the energies reaching PeV. Given that particles are indeed accelerated around microquasars, synchrotron X-rays from primary or secondary electrons are also expected. We have observed the second sub-PeV-brightest microquasar, SS433/W50 with the X-Ray Imaging Spectroscopy Mission (XRISM), whose instruments include the large field-of-view, low-background CCD imager named Xtend. Xtend images of the SS433/W50 region revealed faint diffuse emission in the X-ray dim, "inner cavity" region, within ~16 arcmin from SS433. The excess emission shows a ~0.2 keV optically-thin thermal plasma plus a power-law continuum with a slope of ~1.4. The surface brightness is ~4e-15 erg s-1 cm-2 arcmin-2 in 1–7 keV. The 4.0–5.5 keV X-ray flux varies azimuthally with maximals corresponding to the jet directions, while 1–2 keV, likely thermal X-rays, do not show clear modulations. This excess X-ray emission near SS433 may originate from some energy dissipation processes in the jet, which is possibly related to the sub-PeV emission as well.

Speaker: Hiromasa Suzuki (University of Miyazaki)

93 HAWC Time-Dependent Analysis of the Gamma-ray Binary HESS J0632+057

Gamma-ray binaries exhibit variable high-energy emission driven by interactions between a compact object and its massive stellar companion. Their orbitally modulated emission provides an opportunity to investigate particle acceleration under dynamically changing astrophysical conditions. HESS J0632+057, discovered by the High Energy Stereoscopic System (H.E.S.S.) in 2007, is a Galactic gamma-ray binary with a known orbital period of approximately 315 days.

In this work, we perform a time-dependent analysis of HESS J0632+057 using 2,886 days of data collected by the High Altitude Water Cherenkov (HAWC) observatory. HAWC is a ground-based gamma-ray detector located in Mexico that continuously monitors the overhead sky with a wide field of view (~2 sr) and a duty cycle exceeding 95%. These characteristics make HAWC particularly well suited for long-term studies of variable sources. Using nearly eight years of continuous observations, we achieve uniform phase coverage over multiple orbital cycles, enabling a consistent comparison of emission states and a search for orbital modulation in the very-high-energy (VHE) regime.

We divide the dataset according to the orbital phase of HESS J0632+057 into four emission states, namely, first high state, low state, second high state, and medium state, and construct phase-folded sky maps for each interval. We observe enhanced gamma-ray emission during the two high states. We report the corresponding VHE gamma-ray flux measurements as well as flux upper limits for the low and medium states. We also compare them with phase-resolved results from imaging atmospheric Cherenkov telescopes. In addition, we examine the spectral properties to search for evidence of phase-dependent spectral variability.

Speaker: Chang Dong Rho (Sungkyunkwan University)

94 Investigating TeV Gamma-ray Emission around GRS 1915+105 with HAWC

Microquasars are a subclass of X-ray binaries that host relativistic jets and are considered potential Galactic emitters of very-high-energy (VHE; 0.1–100 TeV) gamma rays. Based on the mass of the companion star, they are categorized into high-mass and low-mass systems, with the latter remaining relatively unexplored in the TeV regime. GRS 1915+105 is one of the most well-known low-mass microquasars, known for its superluminal jets, making it a promising target for VHE studies.
In this work, we analyze approximately 2,886 days of data collected by the High-Altitude Water Cherenkov (HAWC) Observatory to investigate gamma-ray emission in the region surrounding GRS 1915+105. Located near the Galactic plane, this region contains multiple potential counterparts, making source identification challenging. To address this, the analysis accounts for nearby sources and diffuse background contributions and explores a range of morphological and spectral models to characterize the emission. We identify three gamma-ray source candidates in the GRS 1915+105 region and examine their spatial and spectral properties. Among them, one source is spatially associated with GRS 1915+105. We present preliminary results from these analyses and discuss possible interpretations of the observed emission in the context of particle acceleration and radiation processes in low-mass microquasar environments.

Speaker: Minji Shin

95 Studies of the LHAASO Peanut region with VERITAS

The LHAASO “Peanut” is a composite and off-Galactic plane ultra-high-energy gamma-ray source that is among the most intriguing sources released in the 1LHAASO catalogue. The region, which includes a diffuse strip and point-like sources LHAASO J0216+4239, LHAASO J0207+4300, spans nearly five degrees in extension. Currently, there exists no identified multiwavelength counterpart to the Peanut, likely due to both its large extent and the lack of coverage of off-Galactic-plane regions in many existing archives. Diverse models have attempted to describe the Peanut region, such as a “mirage” pulsar wind nebula driven by the nearby millisecond pulsar (PSR J0218+4232), a microquasar outflow from an unidentified central engine, or perhaps a new source class altogether. Although many of these proposed models provide a plausible description of the LHAASO TeV data, the engine and acceleration mechanisms can only be isolated by identifying a multiwavelength counterpart at lower energies or deeply constraining a lack thereof. Imaging Atmospheric Cherenkov Telescopes (IACTs), such as VERITAS, are well-suited to search for this lower energy counterpart due to their large field of view, finer spatial resolution, and overlapping energy range with LHAASO. Here, we present the first IACT results on the Peanut region and its components, including a comprehensive VERITAS spectromorphological analysis of the full Peanut region. In addition, we present a deep study of the putatively associated PSR J0218+4232 at TeV energies and a detailed Fermi-LAT analysis of the Peanut region. We also expand on one-zone leptonic and hadronic spectral modelling of the source using LHAASO, VERITAS and Fermi-LAT data. Together, these analyses supplement the physical interpretations beyond what is possible with LHAASO data alone, in an effort to understand the nature and acceleration mechanisms of this mysterious source and inform the prospects for detection with CTAO.

Speaker: Samantha Wong (McGill University)

MM: MM3 : Transients and Future Multimessenger Missions

96 Neutrino and electromagnetic signatures from superluminous supernovae (SLSNe)

Superluminous supernovae (SLSNe) are rare transients that are $\sim 10 - 100$ times more luminous than ordinary stellar explosions, reaching peak optical luminosities $\sim 10^{44} - 10^{45}$ erg s$^{-1}$. The energy source powering SLSNe remains uncertain. In this talk, I will discuss the multi-wavelength and multi-messenger signatures from the scenario in which SLSNe are powered by a newly born millisecond magnetar. In particular, I will present the thermal and non-thermal electromagnetic and neutrino signatures. Interestingly for SN 2017egm, the nearest observed SLSNe, our prediction for high-energy gamma rays, matches the recent detection by Fermi LAT. I will show that, in the era of the Vera C. Rubin Observatory, a stacking analysis with upcoming neutrino observatories can lead to a $3\sigma$ detection significance of neutrino events from a population of SLSNe within a decade of operation.

Speaker: Mainak Mukhopadhyay (Fermi National Accelerator Laboratory (Fermilab), Kavli Institute for Cosmological Physics (KICP), University of Chicago)

97 Recent results on the prompt GRB emission modelling: properties of the X-ray emission

The multi-wavelength observations of gamma-ray bursts provide insights into the physical conditions in the relativistic jets responsible for their emission. I will discuss new X-ray observations and present the properties of X-ray emission computed in the standard GRB framework of internal shocks. Numerical simulations of the emitted spectrum in the comoving frame performed for a large parameter space, and the spectra/light curves modelled for several representative cases will be shown. I will discuss how these results may contribute to solve some puzzling problems raised by recent GRB observations in X-ray range.

Speaker: Zeljka Bosnjak (FER-University of Zagreb)

98 High-z Gamma-ray bursts Unraveling the Dark Ages and extreme space-time Mission—HiZ-GUNDAM

HiZ-GUNDAM is a candidate for JAXA’s competitive medium-class mission program, with its concept approved by ISAS/JAXA in 2018. This proposed satellite aims to play a leading role in time-domain astronomy in the 2030s by pursuing two primary scientific goals: (1) probing the early universe through the detection of high-redshift gamma-ray bursts (GRBs) and (2) enabling the rapid identification of X-ray and optical-near-infrared counterparts of multimessenger sources. To achieve these objectives, HiZ-GUNDAM is equipped with two key instruments.
A wide-field X-ray monitor, EAGLE, utilizes a micropore optics array and a focal plane imaging sensor to observe transients across ∼0.5 sr in the 0.4 to 4 keV energy range. To follow up on this observation, an optical–near-infrared telescope, MONSTER, features a 30 cm aperture and conducts simultaneous five-band photometry over the 0.5 to 2.5 μm wavelength range. It employs a Kösters-type prism for multi-band photometry to follow up on transients detected by the EAGLE. A sunsynchronous dawn–dusk orbit has been selected to ensure thermal stability for the MONSTER. We present a comprehensive overview of the HiZ-GUNDAM mission concept. The mission is expected to make a significant contribution to our understanding of cosmic evolution through observations of high-redshift GRBs, as well as to the identification of the multiwavelength properties of multimessenger sources by enhancing the observational capabilities for transient searches. The specifications and concepts discussed herein are subject to refinement as the mission progresses.

Speaker: Daisuke Yonetoku (Kanazawa University)

99 MONSTER: Optical and Near-infrared Telescope onboard HiZ-GUNDAM

The High-z Gamma-ray Bursts for Unraveling the Dark Ages Mission (HiZ-GUNDAM) is dedicated to time-domain and multi-messenger astronomy, focusing on the observation of high-energy astronomical transient events, such as gamma-ray bursts (GRBs). HiZ-GUNDAM is designed to deliver rapid alerts of high-redshift GRBs through the use of its wide-field X-ray monitor, the Exploration of Ancient GRBs with Lobster Eye (EAGLE), and a co-mounted 30-cm Multiband Optical and Near-infrared Simultaneous Telescope for Efficient Response (MONSTER), which performs immediate photometric follow-up observations. Upon detecting a transient object, the HiZ-GUNDAM satellite is going to autonomously adjust its attitude toward detected transient events, initiate follow-up observations using MONSTER, and transmit alert information, detailing the object’s position, apparent magnitude, and photometric redshift within 1 h of detection. The MONSTER instrument achieves simultaneous five-band observations in the 0.5 to 2.5 μm range using a beam splitter and a Kösters prism. The incoming light is divided into visible (0.5 to 0.9 μm) and near-infrared components by the beam splitter, with the visible light directed to a visible light detector. The near-infrared light is further divided into four bands (0.9 to 1.3 μm, 1.3 to 1.7 μm, 1.7 to 2.1 μm, and 2.1 to 2.5 μm) by the Kösters prism and detected by a near-infrared detector. To ensure optimal performance, the telescope, beam splitter, Kösters prism, and visible-light detector are cooled to temperatures below 200 K, whereas the near-infrared detector is further
cooled to below 120 K through radiative cooling. In addition, all mirrors and structural components of the telescope are constructed from the same aluminum alloy to minimize alignment errors during the cooling process. We provide an overview of the current status of the conceptual study of MONSTER onboard the HiZ-GUNDAM satellite.

Speaker: Kohji Tsumura (Tokyo City University)

100 The MeV Gamma-ray Sky Forecast: A Predicted All-Sky Map and a Source Catalog for Future MeV Missions

The MeV gamma-ray sky remains the least explored window in high-energy astrophysics, therefore refered to as the “MeV gap”, with only 32 steady sources and 31 GRBs detected by COMPTEL. With COSI launching soon and other future MeV missions, it is now essential to provide quantitative predictions of what these missions will be detectable to strengthen MeV gamma-ray science cases in the multi-messenger era. We present the most comprehensive forecast of the 1–10 MeV sky to date. Building on Tsuji et al. (2021), which cross-matched the Swift/BAT and Fermi/LAT catalogs, we have constructed an updated joint catalog using the latest BAT and LAT releases, substantially expanding the sample. For each source, including blazars, radio galaxies, pulsars, PWNe, SNRs, and globular clusters, we have built phenomenological spectral models from hard X-ray to GeV gamma-ray energies and estimate flux in the 1–10 MeV range. Approximately 200 promising targets exceeding $10^{-11}\ \rm{erg/cm^2/s}$ are found, which is an increase from the 87 sources reported in a previous study. Furthermore, predicted all-sky maps in the 1–10 MeV band have been produced by combining these with Galactic diffuse and extragalactic background emission. I will present the expanded catalog, the all-sky maps, and the impact on multi-messenger and high-energy astrophysics.

Speaker: Michiyasu Nagasawa (Kanagawa University)

NU: NU2 : Detectors and Calibrations

101 The P-ONE Data Acquisition System

The Pacific Ocean Neutrino Experiment (P-ONE) is a planned cubic kilometer neutrino observatory located in the northern Pacific Ocean off the coast of British Columbia, CA. The goal of P-ONE is to detect high-energy astrophysical neutrinos and pinpoint their sources by reconstructing their paths through the detector. P-ONE will consist of ~70 1 km long strings spaced 80 m apart. Each string will be instrumented with evenly spaced modules containing photomultiplier tubes (PMTs) to detect Cherenkov radiation from neutrino interactions in the water. To achieve the goals of path reconstruction and particle identification, the data acquisition system is designed to aim for precision timing (100 ps or better) of multiple photons per PMT. This is done using custom on-module hardware, precision timing distribution throughout the detector, and robust data collection software to handle a non-trivial raw data rate of 100 Tbit/s. This talk will focus on the design and testing of the P-ONE data acquisition system.

Speaker: Jeanne Garriz (Michigan State University)

102 In-Situ Afterpulse Modeling in IceCube

Neutrino point-source searches with IceCube rely on accurate directional reconstruction, requiring realistic simulation of all pulse types in the detector. Afterpulses, delayed secondary pulses in photomultiplier tubes caused by ionization of residual gas, are currently simulated based on laboratory measurements rather than in-ice data, and may not fully capture detector-specific behavior. This limitation is particularly important for high-energy events, where large photoelectron yields can produce more afterpulses and bias the charge and timing information used for directional reconstruction. In this work, we perform an in-situ study of afterpulses using IceCube data and develop an improved model for their time and charge distributions, enabling more realistic afterpulse treatment in simulation.

Speaker: Taeyun Kim

103 A Cost-Effective Optimization of the hybrid-DOM Design for TRIDENT

TRIDENT is a proposed multi-cubic-kilometer deep-sea neutrino telescope in the South China Sea. In this talk, we first present the status of the TRIDENT Phase-I hybrid Digital Optical Module (hDOM), whose baseline design consists of 31 3-inch PMTs and 21 SiPM arrays. We then report an optimization study for future hDOM designs, based on a candidate configuration with 19 4-inch PMTs and 5 SiPM arrays, with the presented study focusing on the PMT system. We compare 3-inch and 4-inch PMT-based configurations using full-chain simulations that include site-specific seawater optical properties and realistic optical backgrounds. Their performance is evaluated in terms of neutrino detection efficiency, directional reconstruction, and ντ identification over the energy range from 1 TeV to 10 PeV. Our results show that 4-inch PMTs with quantum efficiency comparable to that of 3-inch PMTs can provide similar or better physics performance, while reducing channel count, power consumption, and cost.

Speaker: Hengbin Shao (Tsung-Dao Lee Institute，TDLI)

104 Development of a real-time in-situ calibration system for deep-sea neutrino telescopes

Neutrinos can escape extremely dense astrophysical environments, making them unique probes of cosmic-ray origins and fundamental physics. In water-based neutrino detectors, the longer optical scattering length can offer better pointing resolution than in ice. However, this advantage comes with rapidly varying environmental and detector conditions. Variations in water optical properties, detector geometry and intrinsic detector response can bias event reconstruction and reduce physics sensitivity if not properly calibrated.

This talk presents a novel in-situ calibration system for deep-sea neutrino telescopes, currently being implemented for the TRopIcal DEep-sea Neutrino Telescope (TRIDENT). A dedicated calibration string is being designed for real-time monitoring of detector conditions, incorporating: (i) CMOS imaging to measure the water attenuation length; (ii) characterisation of optical background intensity and variability using multiple complementary sensors; (iii) inter-detector timing offset measurements with LED flashers and plastic-scintillator-based muon tagging; and (iv) hydrographic sensors to support the acoustic positioning system. The resulting impact on reconstruction performance for both track-like and cascade-like events will be discussed.

Speaker: Tailin Zhu (TDLI, SJTU)

105 Development of a Fiber Optic Module (FOM) for improving Veto capability in IceCube-Gen2.

The IceCube-Gen2 experiment is a planned expansion of the current IceCube Observatory located beneath the Amundsen-Scott South Pole Station. By increasing the instrumentation volume to approximately 8\text{km}^3 eight times that of the existing detector—and integrating an in-ice optical sensor array with a surface radio array, the project aims to enhance sensitivity in the high-energy regime by a factor of ten. This expansion is expected to identify sources of cosmic neutrinos and drive significant breakthroughs in multi-messenger astronomy.
 In this study, we are developing the Fiber Optic Module (FOM), a light-collection device designed to increase the effective detection area of the Gen2-DOM (Digital Optical Module), which detects Cherenkov light generated in the ice. The FOM consists primarily of scintillating fibers that convert incident Cherenkov light into scintillation light and guide it to the Gen2-DOM. Our development goal is to achieve an effective area for the FOM that is comparable to or greater than that of the Gen2-DOM itself. A key feature of the FOM is its external placement, allowing for installation without modifying the existing configuration or layout of the Gen2-DOMs. We evaluated the optical characteristics of the FOM, including fiber attenuation length, wavelength shifting efficiency, and transmission efficiency, through a combination of experimental measurements, Geant4 simulations, and numerical calculations. Based on these results, we refined the design of the FOM prototype and quantitatively assessed the improvement in the Gen2-DOM's effective detection area through simulations.

Speaker: Keita Yuasa (Osaka Metropolitan University)

3:30 PM break

CR: CR3 : Modeling of Galactic Cosmic-Rays

106 The impact of the eROSITA bubbles on Galactic cosmic-ray transport

We propose that the observed spectral hardening in Galactic cosmic ray fluxes is governed by macroscopic Galactic outflows, such as the eROSITA bubbles, rather than microphysical variations in their scattering properties. Employing a phenomenological transport model, we show that an advective outflow boundary naturally reproduces the $300\,$GV hardening in secondary-to-primary ratios. Global fits to precision AMS-02 data yield an effective local inner halo boundary of $\sim 5\,$kpc and an outflow speed of $\sim 360\,$km/s, in striking agreement with independent multi-wavelength kinematic constraints of the eROSITA outflows. This interpretation provides a testable alternative to breaks in the effective diffusion coefficient, without increasing the number of free parameters.

Speaker: Benedikt Schroer (University of Chicago)

107 Cosmic-ray transport in the multiphase galactic halo: Local spectral hardening in Fermi bubbles

The Fermi bubbles are giant bipolar structures in the Galactic halo. Their formation mechanism and the origin of their hard gamma-ray spectrum remain unclear. Most interpretations have regarded the bubbles as evidence of past Galactic center activity, with leptonic models proposed to explain the hard gamma-ray emission. More recently, some scenarios suggest that the FBs arise naturally from long-term Galactic evolution, in particular through cosmic ray (CR)-driven Galactic winds (Shimoda & Asano, 2024; Sands et al., 2025), with the gamma-rays arising from hadronic interactions. A key difficulty of this scenario, however, is that cosmic rays injected from the disk are expected to soften during transport, implying that some mechanism for spectral hardening in the halo is required. To address this issue, we focus on a multiphase Galactic halo in which hot outflows coexist with cold molecular clouds. In fact, recent observations of cold molecular gas in the Galactic nuclear outflow by Di Teodoro et al. (2020), although not directly aimed at the Fermi bubbles, suggest that the halo may be a multiphase environment rather than a uniform hot wind.
　We investigate the evolution of cosmic-ray spectra in the interaction region between a Galactic wind and molecular clouds, using our two-dimensional CR-hydrodynamics simulation code that self-consistently follows cosmic-ray evolution in momentum space. Focusing on cloud size scales relevant to the molecular gas observed in the Galactic nuclear outflow, we explore how wind--cloud interactions modify the GeV-TeV hadronic gamma-ray spectrum expected in Galactic-wind scenarios. Our calculations show that radiative cooling forms transition layers at wind--cloud interfaces, where cosmic rays are locally heated and concentrated. Advection and diffusion then transport these cosmic rays into molecular clouds, enhancing the high-energy hadronic gamma-ray emissivity. These results suggest that wind--cloud interactions in a multiphase Galactic halo can provide localized sites of gamma-ray spectral hardening and may contribute to the sustained emission associated with the Fermi bubbles.

Speaker: Ryohei Inamoto (ICRR, The University of Tokyo)

108 Where do cosmic rays go to die?

Most ~1-10 GeV hadronic cosmic rays accelerated in star-forming galaxies will eventually escape the relatively dense ISM gas and leak into the circumgalactic medium (CGM). What happens to them thereafter and do they do anything important in this low density environment? I will show that these CRs are, in fact, important: using a new semi-analytic model we have developed over the last few years I will show that CRs, accumulated over the last few Gyr of star formation, contribute non-negligibly to the pressure (gradient) in the CGM of L* galaxies like the Milky Way. I will further demonstrate that the same CR population is important in maintaining the temperature of the CGM via streaming heating. Finally, I will show that the isotropic gamma-ray flux measured by Fermi receives a non-negligible contribution from hadronic emission of CRs in the CGM of all galaxies on our lightcone. IGRB measurements therefore constrain the parameters governing transport of ~1-10 GeV CRs in the CGM.

Speaker: Roland Crocker (Australian National University)

109 Diffusive or Ballistic? Distributions and Spectra of PeV Cosmic Rays around Microquasars

In the standard Galactic cosmic-ray (CR) paradigm, protons are accelerated up to $\sim 1$~PeV by Galactic sources. While supernova remnants (SNRs) have been traditionally considered as the primary accelerators, recent observations by LHAASO and HAWC have detected very-high-energy (VHE) gamma rays exceeding 100~TeV from several microquasars, suggesting that these X-ray binaries can accelerate CRs beyond 1~PeV. We investigate the escape process of CRs from microquasars, focusing on the energy-dependent transport mechanisms. High-energy CRs are likely to have long mean free paths and move ballistically on scales smaller than their mean free path, while lower-energy CRs undergo diffusive propagation. This transition results in a spectral break in the CR distribution around the microquasar. We calculate CR energy spectra within a 10--30~pc radius for various diffusion coefficients and timescales. Our model predicts a spectral break and hardening at $E_p \sim 10$--100~TeV when the standard diffusion coefficient for the interstellar space is assumed. However, current VHE gamma-ray observations do not show clear spectral breaks, suggesting that the diffusion coefficient may be significantly reduced near microquasars, possibly due to magnetic field amplification by CR-driven turbulence.

Speaker: Prof. Yutaka Fujita (Tokyo Metropolitan University)

110 Modeling Cosmic-Ray Transport and Nonthermal Emission in the Jets of SS 433: A Spatially Dependent Approach

The X-ray binary system SS 433 launches mildly relativistic jets that extend over several tens of parsecs. The nonthermal emission detected from the jets is best explained by multi-TeV electrons producing X-ray synchrotron and inverse Compton emission of TeV gamma rays. The LHAASO detection of ultra-high-energy ($>$100 TeV) gamma-ray emission further establishes SS 433 as a potential PeVatron. A proper understanding of the conditions required for accelerating particles to PeV energies calls for detailed modeling of the full X-ray and gamma-ray dataset.

We construct a spatially dependent, one-dimensional cosmic-ray transport model for the jets of SS 433 that allows us to model the nonthermal emission. While we adopt a steady jet model, we reproduce a wide range of observational results, including the energy-dependent morphology of the emission regions in both the X-ray and gamma-ray bands. We report the theoretical implications of our findings, such as the required acceleration efficiency and its relation to the Bohm limit. Our results demonstrate the importance of a spatially dependent approach for understanding extreme Galactic particle accelerators.

Speaker: Mr Tatsuki Fujiwara (The University of Osaka)

DM: DM4 : Indirect Detection and Multi-Messenger Searches

111 Multiwavelength Indirect Dark Matter Searches With Radio- and Gamma-Ray Astronomy

Over the last few decades, dwarf spheroidal galaxies (dSphs) have emerged as prominent targets for indirect dark matter searches in both the radio and gamma-ray regimes due to their high mass-to-light ratio. While gamma-ray observatories, such as MAGIC, search for secondary photons from weakly interacting massive particle (WIMP) annihilation or decay, radio observatories, such as LOFAR, probe the synchrotron emission of the accompanying electrons and positrons. Combining both approaches allows further constraining the WIMP parameter space.

In this work, we adapt the deep-learning-based image reconstruction framework, radionets, for dSph candidates in the radio regime. Further, we employ a recently developed 3-dimensional (spatial + energy) likelihood analysis for dark matter searches with the MAGIC telescopes. Both analyses are discussed alongside the prospects for combined WIMP constraints from radio and gamma-ray observations.

The talk focuses on the sensitivity improvements achieved by combining radio and gamma-ray observations to constrain the WIMP parameter space.

Speakers: Mr Anno Knierim (TU Dortmund University), Felix Wersig (TU Dortmund University)

112 Composite asymmetric dark matter: multi-messenger study

Asymmetric dark matter (ADM) explains the present DM abundance by asymmetry between DM particles and anti-particles, like visible matter or standard model (SM) baryons.
It is particularly interesting when the visible and dark asymmetries have a common origin, since their abundances are different only by a factor of ~5.
In such a case, DM mass should be 1-10 GeV.
ADM is naturally realized by a dark sector strong dynamics like SM QCD, where a composite particle, dark baryon, is DM.
In this talk, we first illustrate how a composite ADM scenario works, by stressing roles of high-energy and low-energy portals.
The high-energy portal, which equilibrates asymmetries in the early Universe, may lead to a smoking-gun signature such as ~1 GeV monochromatic antineutrino flux from ADM decay.
At the same time, the low-energy portal, which releases an entropy from dark sector to SM sector, may lead to ~1 GeV electrons, positrons and gamma rays from the same ADM decay.
In the second part of the talk, we discuss multi-messenger constraints of ADM decay signals.

Speaker: Ayuki Kamada (University of Warsaw)

113 Multi-Messenger Signatures of Dark Matter in Blazar jets

Blazars are a subclass of active galactic nuclei (AGN), the brightest continuously emitting sources in the Universe, powered by accreting supermassive black holes (SMBH). Their defining characteristic is the presence of powerful, back-to-back relativistic jets of protons and electrons, with one jet closely aligned in the direction of Earth. This offers a unique opportunity to probe physics Beyond the Standard Model. The jet can in fact interact with the surrounding Dark Matter in the host galaxy’s halo, offering compelling direct and indirect detection prospects. We present, for the first time, a self-consistent implementation of Dark Matter-proton interactions into a dedicated astrophysical code to quantify this effect. A key signatures of this interaction is the production of high-energy neutrinos and gamma-rays as secondary products of the proton disintegrating in the collision, which can significantly alter the observed spectra of these objects for a large part of unexplored light Dark Matter parameter space. We discuss the reach of this effect and the extent to which it can contribute to the observed astrophysical neutrino flux.

Speaker: Andrea Giovanni De Marchi (Università di Bologna and INFN)

114 Legacy analysis of Milky Way dwarf spheroidal satellite galaxies: an update

Dwarf spheroidal satellite galaxies (dSphs) of the Milky Way are targets of great interest for searches of Dark Matter (DM) signatures with the Fermi-LAT. In the last decade the number of detected and putative dSphs has been rapidly increasing, allowing for some of the most stringent constraints to be put on models of annihilating DM in the GeV-TeV range. The most recent results even highlight the presence of local significance excesses at the 2-3 sigma level.
With the recent observations of ultra-faint compact stellar systems (UFCSs), that might be the darkest galaxies ever observed, and the predictions on the upcoming results of the Legacy Survey of Space and Time (LSST), which poses to double or more the sample of known dSphs over the next decade, we stand before a fundamental moment for gamma-ray searches of DM signatures.
In this work, we apply key improvements to the analysis of the dSphs. We use stricter cuts on the data, implement a method to adaptively model the background, and assume an updated framework for DM annihilation. We find that our improved background modeling leads to a better agreement between the model and the data. This produces an increase in the local and global significance of the dSphs excess compared to previous studies. Finally, we find that the DM properties obtained in this work are less dependent on the sample of dSphs being considered, while remaining in agreement with the predictions from the Galactic center excess observed by theFermi- LAT and the antiproton excess observed by the Alpha Magnetic Spectriometer (AMS-02).

Speaker: Antonio Circiello (Clemson university)

115 Primordial Black Hole evaporation signal searches with MAGIC

Primordial Black Holes (PBHs) remain an interesting candidate for dark matter. Hypothesized to have been formed in the early Universe from the collapse of density fluctuations or other mechanisms, unlike astrophysical black holes, PBHs could span an extremely wide range of initial masses, from about $10^{-5}\, \rm g$ up to $\sim 10^{38}\, \rm g$. Observational constraints from cosmological and astrophysical probes have excluded PBHs as a dominant fraction of dark matter over most of this mass range, leaving only a few viable mass windows, most notably the so-called asteroid-mass range $\sim 10^{17}\,\rm g \,–\, 10^{22}\,\rm g$. In the most simple scenario of Schwarzschild PBHs, those with initial masses around $10^{15}\,\rm g$ are expected to complete their evaporation in the present epoch through Hawking radiation. As the black hole loses mass the evaporation accelerates in a runaway process, culminating in a short and intense burst of very-high-energy particles detectable by gamma-ray experiments.
In this talk we report on the search for gamma-ray emission between 70 GeV and 15 TeV from PBH evaporation using approximately 3000 hours of archival observations from the MAGIC telescopes. This analysis incorporates updated PBH emission scenarios, including non-zero spin (Kerr) PBHs and the recently proposed memory-burden effect. These effects modify the expected evaporation timescale, widening the range of initial PBH masses probed with this method.

Speaker: Elia do Souto (CIEMAT)

116 Probing Dark Matter annihilation in the Galactic Centre with TRIDENT

Next-generation neutrino telescopes have emerged as a powerful tool for constraining dark matter properties in the high-energy regime, which remains largely unexplored. We forecast the sensitivity of the TRIDENT neutrino telescope to dark matter annihilation in the Galactic Centre over the mass range from $10^3$ to $10^5$ GeV, showing that TRIDENT will probe annihilation rates down to $\langle\sigma v\rangle\approx5\times10^{-27}\,{\rm cm}^3\,{\rm s}^{-1}$ for a $10\,{\rm TeV}$ dark matter. The analysis is carried out with all-flavour neutrino interactions, showing that cascade-like events, primarily induced by $\nu_{e,\tau}$, provide a promising channel for dark matter searches compared to the more commonly studied track events. We also highlight the impact of a previously overlooked background, Galactic neutrinos produced from interactions between hadronic cosmic rays and interstellar gas, which can affect the interpretation of a potential signal, especially at high energies.

Speaker: Yingwei Wang (Tsung-Dao Lee Institute，TDLI)

GR: GR4 : SNe and IACT methods

117 Probing Explosive Transients at Very High Energies: Joint LST-1 and MAGIC Observations of SN 2023ixf and TDE 2025aarm

Explosive transients, such as core-collapse supernovae (CCSNe) and tidal disruption events (TDEs), are among the most energetic phenomena in the universe and are prime candidates for efficient particle acceleration up to very-high-energies (VHE; E>100 GeV).
The joint configuration of the Cherenkov Telescope Array Observatory’s (CTAO) first Large-Sized Telescope (LST-1) and the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes offers unparalleled sensitivity in the tens of GeV to TeV energy range, providing a unique window into the non-thermal processes of these events.
In this contribution, I will present results from two of the latest VHE observational campaigns conducted for explosive transient sources:

SN 2023ixf: One of the closest and brightest CCSNe discovered to date. I will present the observations and preliminary results from the most extensive observational campaign ever conducted at VHE for a CCSN, spanning between 2 and 420 days post-explosion. I will discuss current models of gamma-ray emission from CCSNe and explore how the non-detection of SN 2023ixf constrains the supernova environment and particle acceleration efficiency, providing guidance for future observational strategies, with particular emphasis on multi-wavelength approaches.

TDE 2025aarm: The second closest TDE reported to date (z=0.0136). I will present the deepest and earliest TDE observation campaign conducted with Cherenkov telescopes, totaling approximately 11 hours with LST-1 and 30 hours with MAGIC, covering both the opaque and transparent emission phases relative to the optical peak. I will discuss additional constraints for the non-thermal emission in light of a broad multiwavelength dataset collected for TDE2025aarm.

Authors: A. Simongini, M. Kherlakian, A. Lopéz-Oramas, A. Aguasca-Cabot,S. Inoue, V. Barbosa Martins, A. Carosi, G. Pirola, P. Cristofari, F. Acero, on behalf of the CTAO-LST and MAGIC collaborations.

Speaker: Andrea Simongini (INAF - Observatory of Rome)

118 Advancing the Understanding of Interaction-Powered Transients through Numerical Modeling

Among the diverse population of astrophysical transients, those powered by the interaction between explosive ejecta and circumstellar material (CSM) are of particular interest, not only as electromagnetic transients but also as potential sites of high-energy particle acceleration. Understanding how CSM interaction converts kinetic energy of the ejecta into electromagnetic radiation through detailed comparisons between theoretical models and observations is essential for constraining the conditions under which particle acceleration may occur. In this talk, I focus on core-collapse supernovae exploding within dense circumstellar environments and discuss recent efforts to model their electromagnetic emission using numerical simulations. Shock breakout marks the onset of observable emission and provides a unique probe of energy dissipation occurring at the interface between the outermost layers of the ejecta and the innermost regions of the CSM. Numerical modeling of shock breakout emission has played an important role in constraining both the ejecta structure and the properties of the surrounding CSM. I review the physical processes responsible for the early emission from interaction-powered transients, summarize recent developments in numerical modeling, and discuss implications from several recently observed events.

Speaker: Akihiro Suzuki (University of Tokyo)

119 Interacting supernovae as cosmic-ray factories: simulations and observations

Supernova remnants (SNRs) are generally considered as the main contributors to the Galactic sea of cosmic rays (CRs) on the account of their energy budget. Indeed, they are the only known sources in the Galaxy that are capable of explaining the energy density of CRs at lowest energies. Acceleration of CRs at the shock fronts of SNRs is confirmed by detection of non-thermal emission of radio waves, X-rays, and gamma rays. It is, however, unclear what are the highest energies that can be reached in these objects. There are several reasons to believe that SNRs are the most efficient accelerators during the very initial stages of evolution, right after the explosion, but so far no supernovae (SNe) were detected in gamma-rays despite dedicated observational campaigns. This could be partially due to the observation strategy - the peak of gamma-ray emission for core-collapse (CC) SNe evolving in smooth winds is expected to happen days to weeks after the explosion where most of the emission is attenuated by gamma-gamma interactions with a photosphere. It is known, however, that massive stars such as luminous blue variable (LBV) stars and red supergiants (RSGs) feature circumstellar shells with enhanced density. Interaction of the SN shock with such shells would increase both acceleration efficiency and non-thermal emission. Such episodes of interaction may happen months or years after the explosion where gamma-gamma absorption by photosphere is negligible and gamma-ray emission can be well detectable. In this talk we present numeric simulations of such scenarios and show that current observation strategies for gamma-ray signals from SNe should be re-designed. We propose the multiwavelength observation campaign for transient emission from interacting SNe and report on the status of observational proposals submitted to various instruments. At the time of the abstract submission the campaign already resulted in detection of the radio re-brightening of a supernova 18 years after explosion.

Speaker: Iurii Sushch (CIEMAT, Spain)

120 New Science Cases in IACT Gamma-Ray Astronomy Using Run-Wise Simulations

In ground-based gamma-ray astronomy, discoveries and measurements are often challenged by systematic uncertainties of the applied Instrument Response Functions. In most cases, both existing and planned future instruments rely on pre-generated simulations, where the actual observation and detector conditions are taken into account only to a certain, limited degree. Furthermore, they often assume a simplified geometry of the detector response, leading to even larger systematic uncertainties.
Over the last years, an alternative scheme of simulations that are custom-tailored to the observation conditions and detector settings (Run-Wise Simulations, RWS) has been utilized by the H.E.S.S. collaboration and played a key role in several high-impact results.
In this contribution, we are going to present how RWS can be exploited to reduce systematic uncertainties, increase the sensitivity for detecting faint sources, and thus open up new science cases.

Speaker: Markus Holler

121 Event Level Searches for New Physics with IACTs: Ultra short gamma-ray bursts

The search for beyond the standard model physics with gamma-ray telescopes has traditionally been dominated by searches that leverage the extreme astrophysical environments of high-energy sources. These include searches for unexpected signal deviations (i.e., photon absorption or delay) and/or searches for predictable features (i.e., excesses from dark matter decay/annihilation). Both methods rely solely on studying the small sample of events collected by these telescopes that resemble gamma-ray air showers, discarding potentially interesting air shower images simply because they do not resemble single-photon-induced showers.

Imaging Atmospheric Cherenkov Telescopes (IACTs), such as VERITAS, provide an alternative avenue, utilizing the images of air showers to search not for gamma rays or cosmic rays, but for new particles and/or a unique combination of particles that would normally be removed during standard event selection. Since beginning operations in 2007, VERITAS has measured over 1 billion events, creating a rich dataset for these "rare event" searches. In this talk, we will present the results from such a search, one that is looking for "ultra-short gamma-ray bursts" (UGRBs). UGRBs are theoretical narrow pulses of gamma rays occurring for less than a microsecond. They could originate from pulsars, as fast radio burst counterparts, or as counterparts to macroscopic dark matter interactions. With a sufficient fluence, multiple gamma-rays from a UGRB are expected to produce overlapping air showers. These "wavefront" events provide unique images with features unseen in other air showers. We will present a series of realistic wavefront simulations and demonstrate how IACTs can practically search for such events in pre-existing datasets. Further, we will demonstrate how this time-domain based search performs on real VERITAS data, presenting the first results from a modern search. We will also discuss the potential for future rare event searches with next generation IACTs like LACT and CTAO.

Speaker: Matthew Lundy (Columbia University)

122 CTAO – A New Era for Astroparticle Physics at the Highest Energies

The Cherenkov Telescope Array Observatory (CTAO) will be the first open, proposal-driven research infrastructure for very-high-energy gamma-ray astronomy. With an order-of-magnitude improvement in sensitivity over existing instruments and an energy range extending from a few tens of GeV to several hundred TeV, CTAO will enable transformative studies of the non-thermal Universe.
Operating arrays in both hemispheres, CTAO will provide unprecedented access to the entire gamma-ray sky and will play a central role in the era of time-domain, multi-wavelength, and multi-messenger astrophysics. Even during its early science phase, the observatory is expected to deliver major scientific discoveries across a broad range of topics.
As construction progresses towards the first intermediate array configurations, CTAO is moving toward the start of science operations. This contribution reviews the current status of the project and discusses the scientific opportunities and expected performance of the initial observatory configurations.

Speaker: Ivana Batković (Cherenkov Telescope Array Observatory)

MM: MM4 : Particle Acceleration

123 Acceleration of TeV particles in structure formation shocks

The process of hierarchical structure formation drives powerful shocks through the merger of massive galaxy clusters and the continuous accretion of mass onto cosmic filaments and galaxy clusters. The role of these shocks in the acceleration of GeV to TeV protons and their distribution in the intra-cluster and warm-hot intergalactic medium (ICM and WHIM) is so far not well understood.
I will present our recent advances in self-consistently modeling the acceleration of particles, their advection, and their spectral evolution in cosmological simulations of galaxy cluster formation. We recently studied the impact of the recently introduced potential confinement of CR protons by micro-mirror instabilities in the ICM.
In this talk, I will present follow-up work that studies the volume-filling fraction of shock-accelerated TeV protons in the ICM and their potential observability via diffuse gamma-ray emission.

Speaker: Ludwig Böss (University of Chicago)

124 Particle Acceleration in Weakly Magnetized Transrelativistic Shocks

Astrophysical shocks are considered to be one of the main sources of cosmic rays in the universe. Long-term observations of gamma-ray burst (GRB) afterglows, the recent detection of >100 TeV gamma-rays from microquasars, and the discovery of fast blue optical transients (FBOTs) motivate us to investigate transrelativistic shocks, which are underexplored, in terms of microphysics, compared to ultrarelativistic shocks. Using particle-in-cell (PIC) simulations, we show that magnetic field amplification and particle acceleration characteristics depend strongly on shock velocity and on upstream magnetic field strength. Shocks with a relatively strong upstream magnetic field and a slow velocity accelerate ions efficiently, but the fraction of energy going into nonthermal electrons is small. On the other hand, shocks with a relatively weak magnetic field and a fast velocity accelerate ions less efficiently while converting significantly more energy into nonthermal electrons. We apply our PIC simulation results to the maximum energy of gamma-rays and variability in X-ray emission, both in terms of brightness and thermal/nonthermal origin.

Speaker: Taiki Jikei (Columbia University)

125 Robust 3+1D simulations of BDNK causal relativistic hydrodynamics

Relativistic viscous hydrodynamics is the workhorse for modeling the quark–gluon plasma (QGP) created in high-energy heavy-ion collisions and could play an equally crucial role in understanding hot, dense matter in neutron stars and their mergers. In contrast to commonly used Israel–Stewart–type (IS) theories, which can exhibit acausal behavior, we consider the Bemfica–Disconzi–Noronha–Kovtun (BDNK) formulation, equipped with well-defined causality conditions that are convenient for numerical implementation. We present two independent formulations that enable stable and accurate 3+1D simulations of the BDNK causal relativistic viscous hydrodynamic theory on arbitrary curved spacetimes. Both schemes are rigorously shown to be flux-conservative, strongly hyperbolic, locally well-posed, and mutually equivalent: one is a full first-order reduction augmented with auxiliary fields to enforce constraints, while the other is a mixed-order formulation that forgoes these fields and is more memory-efficient and markedly faster. We outline the underlying ideas and present a comprehensive validation of our numerical implementation through a suite of tests. Convergence and accuracy are demonstrated across all cases, including systems with semi-analytical solutions relevant to heavy-ion collisions and shock-tube benchmarks, with direct comparisons to standard IS-based approaches. In the low-viscosity limit, the code recovers stationary ideal-hydrodynamic solutions, including Bondi–Michel spherical accretion and equilibrium Kerr torus configurations, with negligible deviations from stationarity. We report progress toward developing a unified, open-source, performance-portable, GPU-ready codebase for simulating relativistic viscous fluids across QGP and astrophysical regimes.

Speaker: Teerthal Patel (Vanderbilt University)

126 Origin of Cosmic Rays from the Pre-Structure Universe to Structure Formation Shocks

Understanding the origin and evolution of cosmic rays (CRs) across cosmic time is a key problem in high-energy astrophysics and cosmology. Recent studies suggest that the earliest CRs may have been produced at collisionless shocks driven by the supernova explosions of the first stars at z ~ 20. In this work, we explore a possible scenario for CR production across cosmic epochs, connecting plasma processes in the pre-structure universe to particle acceleration at large-scale structure shocks. In weakly magnetized intergalactic plasmas prior to nonlinear structure formation, large-scale plasma motions naturally generate pressure anisotropy with respect to the background magnetic field. Such anisotropy can drive kinetic instabilities, including mirror and firehose modes, which significantly enhance magnetic-field amplification during cosmological magnetogenesis. As magnetic fields grow, the associated increase in gyrofrequency enhances pitch-angle scattering, potentially enabling stochastic (second-order Fermi) acceleration in turbulent plasma. We investigate the efficiency of this process by comparing the stochastic acceleration timescale with the cosmological expansion timescale and by solving a Fokker–Planck equation for the evolution of the proton distribution. Our results indicate that instability-enhanced scattering can reduce the acceleration timescale, but the resulting particle population remains primarily suprathermal prior to the onset of large-scale structure formation. These suprathermal particles may nevertheless provide seed populations for subsequent diffusive shock acceleration (DSA) at structure formation shocks. In particular, shocks associated with hierarchical structure formation, including strong accretion shocks in cluster outskirts and weaker internal shocks in the intracluster medium, can further accelerate particles and generate observable nonthermal emission in galaxy clusters. We discuss how plasma microphysics operating across different cosmic epochs collectively shapes the origin and evolution of cosmic rays in the Universe.

Speaker: Ji-Hoon Ha (Korea Astronomy and Space Science Institute)

127 SN 1006: a Cosmic Laboratory for Investigating Shock Acceleration Physics

SN 1006 is a historic supernova remnant exhibiting a bilateral shape, with non-thermal X-ray and TeV emission more prominent in two polar cap regions aligned with the ambient magnetic field. Further, a large-scale ambient density gradient is observed to be roughly perpendicular to the magnetic axis. We model the multi-wavelength spectral and spatial properties of each quadrant in SN 1006 using a self-consistent, semi-analytical model of non-linear particle acceleration derived from kinetic plasma simulations, and compare to the latest multi-wavelength observations. Such a spatially-resolved analysis allows us to investigate how CR acceleration depends on shock obliquity and how the hadronic/leptonic nature of gamma-ray emission depends on the ambient density.

Speaker: Emma McGinness (University of Chicago)

128 Exploring Cosmic Rays from Gravity-Limited Acceleration at Supermassive Black Holes

Several theoretical models explain the neutrino flux from Active Galactic Nuclei, such as NGC 1068, as originating from cosmic-ray interactions in the corona. If cosmic rays are destroyed in such dense environments, a natural question arises: where do the observed Ultra-High-Energy Cosmic Rays (UHECR) originate? In this contribution, we explore the possibility that UHECRs originate in transparent environments with low accretion rates. First, we show that horizon-scale magnetic fields threading supermassive black holes (SMBHs), limited only by gravity, can accelerate particles to the highest detected energies and beyond. Subsequently, we build a realistic parameter space in which the environment surrounding the SMBH is transparent enough to allow the primaries to escape, while the magnetic fields remain strong enough to accelerate to Ultra-High-Energies. Finally, we test this hypothesis on UHECR data from the Pierre Auger Observatory by performing a correlation analysis with a list of nearby galaxies with reliably measured masses, differentiating between AGN and quiescent hosts. The analysis shows marginal excesses that are compatible with the background after accounting for the look-elsewhere effect. Nevertheless, the presented framework provides a link between black-hole physics and the maximum energies of cosmic particles and defines concrete observational tests for next-generation UHECR datasets.

Speaker: Elena Manao (TUM)

NU: NU3 : High-Energy Astrophysical Neutrino Measurements

129 The Baikal-GVD Neutrino Telescope: status and recent results

Baikal-GVD is a cubic-kilometer scale neutrino telescope, optimized for
TeV-PeV neutrino energy range, being constructed in the southern part
of Lake Baikal. The detector is a three-dimensional array of hermetic
containers with enclosed PMTs located at depths between 750 and 1275 m
and organized into independent sub-arrays - clusters. Presently the
telescope includes 16 clusters and its sensitive volume is about 0.8
km^3. Neutrinos interacting in the vicinity of the detector are
reconstructed using cascade or track -like event signatures generated
respectively by cascades of charged particles or muons produced in the
interaction and propagating through the detector volume. In the
present report we discuss the status of the telescope and present
first astrophysical results from the incomplete detector. We report on the
measurement of astrophysical neutrino diffuse flux using cascade
events and present neutrino source searches using both cascade and
track -like events and other data analysis results. We discuss the
real-time alert program being developed at Baikal-GVD.

Speaker: Grigory Safronov (INR RAS)

130 The First Long Term In-situ Performance of a Prototype Demonstrator for TRIDENT Neutrino Telescope

The TRopIcal DEep-sea Neutrino Telescope (TRIDENT) is a next-generation neutrino telescope planned in the "Hai-Ling Basin" of the South China Sea at a depth of about 3.5 km. Designed for world-leading sensitivity to high-energy astrophysical neutrinos of all flavours, TRIDENT will instrument a multi-cubic-kilometre volume of seawater with advanced photon-detection technology. As a key step toward its first construction phase, TRIDENT-Explorer 2024 (T-REX 2024), a single-string prototype for TRIDENT, was deployed at the future detector site to test fundamental technologies under realistic deep-sea conditions. Equipped with multiple digital optical modules, the prototype string operated continuously for four months at site, enabling studies of environmental conditions and detector performance over an extended period. In this work, we present the in-situ performance of the T-REX 2024 prototype string. The results provide valuable validation of key TRIDENT detector technologies and establish performance benchmarks for future detector deployment.

Speaker: Fuyudi Zhang (Tsung-Dao Lee Institute)

131 Status of the Pacific Ocean Neutrino Experimen

IceCube has discovered a flux of galactic and extragalactic neutrinos as well as provided evidence for neutrino emission from two active galaxies, NGC-1068 and TXS 0506+056. Nevertheless, the class of objects responsible for extragalactic neutrinos is unknown; the Milky Way flux is due to an unknown combination of individual sources and diffuse flux due to cosmic ray propagation. Answering these questions requires a new generation detector focused on precision measurements via significant improvements in angular resolution. In this talk, I will discuss the status and prospects of the Pacific Ocean Neutrino Experiment (P-ONE), located in the Cascadia basin off the west coast of Canada. With modern instrumentation and longer scattering length in seawater compared to Antarctic ice, a kilometer-scale P-ONE can increase the number of extragalactic sources by an order of magnitude and can prove realistic models for Galactic sources.

Speaker: Ignacio Taboada (Georgia Institute of Technology)

132 POLARIS: A Sparse Radial Neutrino Telescope Design for the Pacific Ocean

We present POLARIS, a new sparse radial detector design for an underwater neutrino telescope. The design targets multi-PeV horizontal tracks with a minimal instrumentation density of around 1000 Digital Optical Modules (DOMs). We evaluate the astronomy potential of this design through 5-sigma point source and diffuse flux detection limit, benchmarking against IceCube, KM3NeT ARCA, TRIDENT, TAMBO and RNO-G, spanning ice, water, and air-shower based detection techniques. POLARIS is an effective design to reach next-generation sensitivity at PeV energies either as a standalone instrument or as an extension of existing or planned underwater telescopes.

Speaker: Karolin Hymon

133 Towards Deep Learning-Based Event Reconstruction and Selection for Point-Source Searches with the IceCube-Gen2 Optical Array.

IceCube-Gen2 is the planned high-energy extension of the current IceCube detector, featuring an optical array nearly eight times larger than that of IceCube and composed of novel optical modules containing multiple photomultiplier tubes (PMTs), providing enhanced and nearly omnidirectional sensitivity. This configuration is expected to significantly increase event statistics and improve the discovery potential for astrophysical neutrino sources. Fully exploiting these advances requires new reconstruction and event selection techniques adapted to the detector geometry and sensor design. In this contribution, we present ongoing work on deep learning-based methods for neutrino event direction and energy reconstruction in the IceCube-Gen2 Optical Array, together with classifiers designed to suppress atmospheric muon bundle background and identify starting events. We discuss the performance of these methods and their potential impact on future point-source searches.

Speaker: Francisco Javier Vara Carbonell (University of Münster)

134 A Joint Characterization of Galactic and Extragalactic Neutrino Fluxes

We present new results from a measurement of the high-energy astrophysical neutrino flux, featuring an explicit separation into the galactic and extragalactic components. We use the energy and directional information from data collected by the IceCube Neutrino Observatory to resolve the spatial structure of the Galactic plane on the sky while simultaneously measuring the isotropic astrophysical flux. The data comprise a combined sample of about 860,000 neutrino-induced muon-track events and 12,700 cascade events. For the galactic neutrino flux, we find that the CRINGE model, scaled by a factor of $2.7 \pm 0.8$, provides the best description among the models considered. A geometric model assuming homogeneous emission from the galactic disc is disfavored at the $3.1\sigma$ level, indicating an enhanced flux towards the galactic center region. Regarding the extragalactic spectrum, we confirm the recently reported change in the spectral index: a single power-law hypothesis is now excluded at $>5\sigma$ in favor of a description with curvature or a spectral break below $\sim30$ TeV.

Speaker: Philipp Fürst (RWTH Aachen University)

Wednesday, September 2

Plenary

135 Einstein Probe and its role in multi-messenger astronomy

The Einstein Probe (EP) is a space X-ray observatory designed to detect mainly high-energy transient and variable sources in the universe. It features a lobster-eye wide-field X-ray monitor with unprecedented sensitivity and spatial resolution in the soft X-ray band, and a conventional X-ray telescope to perform quick onboard follow-up observations. EP is a project led by the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES. Since its launch on January 9, 2024, EP has detected over 200 transients. Among these are more than 150 fast X-ray transients (previously only 30+ had been discovered), offering potential to unravel the origin mystery of such transients. Key scientific achievements include: Detecting the highest redshift fast X-ray transient, challenging conventional jet theories; Capturing several rare intermediate-mass black holes and over a thousand stellar X-ray flares (exceeding the previous global total); the identification of dozens of stellar-mass black holes, neutron stars, and white dwarfs. EP has also performed prompt follow-up observations of several gravitational wave and neutrino events. The scientific potential of EP in the context of multi-messenger astronomy will be discussed.

Speaker: Yuan Liu (National Astronomical Observatories of China)

136 First Results from the SVOM mission on Gamma-ray Bursts and fast transients

The SVOM mission is a French-Chinese cooperation successfully launched in June 2024. The SVOM multi-wavelength space payload is composed by two wide field gamma-ray instruments (ECLAIRs and GRM), and two narrow field instruments, MXT and VT, operating in the X-ray and visible domains.
The space segment is complemented by dedicated robotic telescopes operated from China and Mexico.
In this talk I will review the scientific results from the first two years of the SVOM mission focussing on Gamma-Ray Bursts and other high-energy fast transients.

Speaker: Diego Götz (CEA Saclay - Irfu/Département d'Astrophysique)

10:30 AM break

Plenary

137 Recent highlights of Astrophysical neutrino detection from GeV to EeV

High-energy neutrinos have become a quantitative probe of non-thermal processes in the universe. Over the past decade, cubic-kilometer scale detectors have established a diffuse astrophysical neutrino flux from the TeV to PeV range and identified candidate events reaching the PeV–EeV energies. Recent highlights include the first >5σ discovery of Galactic neutrino emission, indications of spectral structure in the diffuse flux, and increasingly sensitive multimessenger and time-dependent searches targeting active galaxies and transient sources. At the highest energies, optical and radio techniques are extending sensitivity toward the EeV regime, probing connections to ultra-high-energy cosmic rays.
Despite this progress, key questions remain: the origin of the diffuse flux, the identification of Galactic PeVatrons, the contribution of transient sources, and the evolution of neutrino flavor composition with energy. In this talk, I will review recent experimental results across the GeV–EeV range and discuss their implications for particle astrophysics. I will conclude with the status of the IceCube Upgrade and its expected impact on calibration, flavor sensitivity, as well as transient and supernova detection.

Speaker: Lu Lu (University of Wisconsin-Madison)

138 Quantum sensor & wave-like dark matter detection

Superconducting qubits are sensitive to noise - from electromagnetic disturbances, impurities in the material, and even cosmic rays can easily perturb their quantum states and induce errors.
While none of these are desirable from the quantum computer point of view, the high sensitivity implies potential usage as for sensors for exotic weak fields—such as dark matter.
In this talk, I overview the currently explored ideas of sensor application of superconducting qubits, quantum-limit sensing techniques, and the prospect of future experiment designs including the possibility of using quantum computers themselves as dark matter detectors.

Speaker: Shion Chen (Kyoto University)

12:00 PM Lunch

CR: CR4 : Cosmic-Ray Air-Showers

139 Bayesian hierarchical cross-calibration of hybrid air-shower detectors

Calibrating the energy scale of surface detector arrays using fluorescence detector data is a primary source of systematic uncertainty at ultra-high-energy cosmic ray observatories. Standard procedures provide point estimates of the calibration function with no associated uncertainty. We present a hierarchical Bayesian model that introduces the true event energy as a latent variable, allowing measurement noise from both detectors to be accounted for simultaneously while inferring a full posterior over the calibration function. The posterior uncertainty grows naturally at high energies where hybrid coverage is sparse or absent, allowing calibration uncertainty to be propagated into any downstream analysis. The model is validated on synthetic data, demonstrating unbiased recovery of the calibration function and correct posterior coverage.

Speaker: Anton Prosekin (Institute of Physics, Academia Sinica, Taiwan)

140 Gain measurements of eight-inch photomultiplier tubes at field and laboratory toward Fluorescence detector Array of Single-pixel Telescopes

Fluorescence detector Array of Single-pixel Telescopes (FAST) aims to achieve high-statistics observations of ultra-high-energy cosmic rays by deploying a large number of fluorescence telescopes over a wide area for next-generation cosmic-ray experiments. Total seven FAST prototypes are currently installed and operated at sites of the Telescope Array experiment and the Pierre Auger Observatory. The prototypes consists of mirrors, cameras, and electronics. Variations in the characteristics of these components must be properly taken into account of data analysis. Otherwise, they can cause large uncertainties in the reconstructed energy and arrival direction of cosmic rays. FAST is designed for long-term operation over more than 10 years, making it essential to understand the variations in detector performance due to environmental effects and aging. In this study, we analyzed data from the standard light source YAP collected between 2017 and 2025 with operating the FAST prototypes. We also performed gain measurements of the photomultiplier tubes (PMTs) used in FAST through single photoelectron measurements in a laboratory. In this contribution, we evaluate the long-term variation and temperature dependence of the PMT gain in FAST and report on studies toward establishing a reliable calibration method.

Speaker: Haruka Tachibana (Osaka Metropolitan University)

141 Prospects for the measurement of TeV cosmic ray Iron nuclei using Large-Sized Telescope of CTAO

Cosmic-ray chemical composition measurements are important for elucidating the origin of cosmic rays within the galaxy. The iron cosmic-ray spectrum in the TeV band is not yet well-characterized because of large statistical uncertainties, necessitating high-precision measurements in this energy range. TeV iron cosmic-rays can be observed with imaging atmospheric Cherenkov telescope by detecting the Cherenkov light they induce before they start an extensive shower. Since the Large-Sized telescopes (LSTs) of the Cherenkov Telescope Array Observatory are constructed using a larger mirror than in previous studies, it is anticipated to possess high energy and charge resolution, and is expected to demonstrate excellent background removal capabilities. Furthermore, for the same reason, it is expected to enable observations at higher zenith angles, resulting in an increase in effective observation time. For these reasons, LSTs are expected to provide a higher sensitivity as compared to previous studies. We report on the evaluation of the charge reconstruction performance of iron events using Monte Carlo simulations of the array of LSTs, and present the observational conditions under which iron nuclei can be detected. We also report on direct Cherenkov event candidates identified through the analysis of LST-1 real data.

Speaker: Masakaze Mizuno

142 Evaluation of the stereo observation performance with the Fluorescence detector Array of Single-pixel Telescopes

The Fluorescence detector Array of Single-pixel Telescopes (FAST) is a next-generation experiment designed for observing ultra-high-energy cosmic rays (UHECRs). Compared to conventional fluorescence detector, FAST features a compact and low-cost design by reducing the number of photomultiplier tubes. This design allows for the deployment of a large number of telescopes, aiming to achieve an unprecedented aperture. Currently, seven FAST prototypes are operated at two sites: three at the Telescope Array experiment and four at the Pierre Auger Observatory.
In this contribution, we report on evaluations of the stereo observation performance of the four FAST prototypes installed at two locations within the Pierre Auger Observatory using simulations. We address the expected annual event rate and the reconstruction resolution and bias for geometry, energy and $X_{\mathrm{max}}$. Furthermore, there is a future plan to install two additional prototypes at a third location at the Pierre Auger Observatory to form a FAST mini array. We also present the performance evaluation for this configuration based on simulations.

Speaker: Kaho Tanaka (Osaka Metropolitan University)

143 Discriminating Heavy Cosmic Rays via Direct Cherenkov Light

Iron cosmic rays constitute the most common heavy nuclei at energies above 1 TeV and are thought to arise mainly from astrophysical environments. Accurate determinations of their energy spectrum offer essential clues about the origin, acceleration, and transport of cosmic rays. Recent measurements by satellite‑based instruments have shown unexpected spectral features in the GeV–TeV domain; however, their capability at higher energies is constrained by limited statistics.

Beyond a few TeV, ground‑based facilities such as the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes provide a clear advantage thanks to their large effective areas, enabling observations that extend and complement those of space missions. In this study, we apply the direct Cherenkov technique, which leverages the Cherenkov light emitted by primary charged particles before the atmospheric cascade develops, to identify iron‑initiated air showers and distinguish them from events produced by lighter nuclei. With this approach, we determine the energy spectrum of cosmic‑ray iron nuclei at TeV energies using the MAGIC telescopes.

Speaker: Miguel Molero Gonzalez (CIEMAT)

144 Reconstructing a history of Galactic Cosmic Rays from 14CO in Antarctic ice

Measurements of long-lived isotopes in meteoritic data indicate the flux of Galactic cosmic rays (GCRs) has been constant for several Myr, however these measurements may be uncertain by 30% or more, due to confounding factors such as solar and geomagnetic modulation of the GCR flux. $^{14}$C produced in situ by interactions between cosmic ray muons and $^{16}$O atoms in ice can serve as a new proxy for historical GCRs, where the energy requirement for underground muon propagation filters out contamination from low energy solar and geomagnetic variations in the cosmic ray spectrum. We present a model of the relationship between cosmic rays at the top of the atmosphere and radiocarbon monoxide ($^{14}$CO) formed in ice, using atmospheric and in-ice particle cascades. By examining the concentration of $^{14}$CO in shallow ice cores extracted from Dome C, Antarctica, we can reconstruct changes in the GCR flux over a ∼7 kyr timescale with higher precision than other methods. This approach requires accurate characterization of the muon flux in ice, muon interaction cross-sections, and ice accumulation history to track the formation and transport of $^{14}$CO. We show results from archival measurements at Taylor Glacier, Antarctica and discuss preliminary measurements at Dome C and expected constraints on the recent history of the GCR flux.

Speaker: Walter Cook (University of Rochester)

DM: DM5 : Cryogenic and Novel Detection Techniques

145 Illuminating the Invisible: COSINUS Commissioning at LNGS and remoTES Scale-up through PIRATES

COSINUS is a cryogenic, low-background experiment at Laboratori Nazionali del Gran Sasso, designed to provide a model-independent cross-check of the DAMA/LIBRA dark matter modulation claim. It operates ultrapure Sodium Iodide (NaI) crystals as dual-channel cryogenic calorimeters: the remoTES scheme reads out the phonon signal, and a surrounding silicon beaker read out with a traditional Transition Edge Sensor (TES) collects the scintillation light. The light-to-phonon ratio of each event discriminates nuclear recoils from electronic backgrounds. Prototypes have achieved a nuclear recoil energy resolution of 150 eV. With the custom dry cryostat and water Cherenkov muon veto commissioned, data-taking for the first phase of the experiment is scheduled to begin in the second half of 2026.

We also report on PIRATES, the COSINUS-driven fabrication program at the Max Planck Halbleiterlabor (HLL) aimed at scaling remoTES sensor production onto 150 mm silicon wafers to establish the path for larger arrays needed beyond Phase 1.

Speaker: Mukund Bharadwaj

146 Demonstration of eV-Scale Energy Resolution with the remoTES Detector Design

Transition-edge sensors (TESs) are highly sensitive detectors capable of measuring extremely small energy depositions with excellent energy resolution in the sub-eV to eV range. However, the target material of the COSINUS experiment, sodium iodide (NaI), is incompatible with standard TES fabrication processes. To overcome this limitation, the COSINUS collaboration has developed the remoTES design. In this configuration, the TES is fabricated on a separate wafer and thermally coupled to the absorber via a gold link. This physical separation between absorber and sensor offers several advantages, including compatibility with a wider range of materials that could not previously be employed as cryogenic calorimeters. Furthermore, this approach enables scalable and reproducible TES fabrication on a dedicated wafer material, facilitating the mass production required for next-generation large-scale rare-event searches. In this contribution, we present recent R&D results demonstrating that the remoTES design achieves an energy resolution comparable to conventional TES detectors, reaching the eV scale. This performance opens the possibility to probe the low-energy excess using the remoTES design.

Speaker: Kumrie Shera (Max Planck Institute for Physics)

147 Demonstration of new analysis tools developed in the COSINUS collaboration

The COSINUS experiment aims at the direct detection of dark matter, operating sodium iodide crystals as cryogenic calorimeters using the remoTES design. In this design, the TES is deposited on a seperate wafer and connected to the phonon collector on the absorber via a gold bonding wire. The resulting pulse shape upon a particle interaction is well described by a three-node thermal model.

To gain a more in-depth understanding of the detector physics, a Bayesian pulse-shape inference framework using BAT.jl was developed and validated on several prototypes. The configuration of the framework allows for the accommodation of posterior distributions for parameters such as thermal response and collection efficiency. These parameters are instrumental in quantifying phonon propagation and detector response. Consequently, this framework facilitates applications including detector diagnostics and event-type classification.

To address the increasing volume of data from large detector arrays, automated analysis modules have been developed. The purpose of these modules is twofold: firstly, to streamline data processing, and secondly, to reduce manual intervention. The development of all these modules was implemented using a low background data set from a COSINUS measurement conducted at LNGS. Subsequently, the performance was validated using above-ground detectors that exhibited a considerably elevated background and noise level.

It has been demonstrated that the modules possess the capacity to generate a noise power spectrum(NPS) entirely autonomously.A comparison of this NPS with a handmade NPS shows no significant difference. Furthermore, they employ a neural network to facilitate the cleaning of data. This is followed by a process of event type classification, which results in the generation of a standard event for each event type, thereby obviating the need for human intervention.

Speaker: Maximilian Gapp (COSINUS-Experiment)

148 Probing Photon–Magnetic Field Coupling via High-Resolution $^{241}$Am Spectroscopy with a CeBr$_3$ Detector

The search for axion-like particles (ALPs) and other weakly interacting states remains an important problem in particle astrophysics. One possible production mechanism is the Primakoff effect, where photons can convert into weakly interacting particles in the presence of an external magnetic field.

In this work, we investigate whether a photon beam passing through a magnetic field can lead to measurable changes in the decay spectrum of $^{241}$Am. The idea is that particles produced in the magnetic field may interact with the radioactive source and induce small deviations in the observed gamma-ray spectrum.

The experimental setup consists of a photon beam propagating through a magnetic cavity, followed by a $^{241}$Am source. Data are collected in two configurations: a “light” mode (sP), where the beam passes through the magnetic field, and a “dark” mode (sD), where the beam is blocked. A differential comparison between these two modes is used to search for possible effects associated with photon–magnetic field interactions.

The measurements are performed using a CeBr$_3$ detector, which provides improved energy resolution and lower background. This allows for a more precise study of the 59.54 keV gamma line and makes it possible to probe small differences in the spectrum.

Preliminary results from ongoing measurements show indications of small differences between the two modes. Further analysis is in progress to evaluate their statistical significance and to study their dependence on magnetic field orientation. This approach provides a controlled way to test photon–magnetic field coupling and its possible connection to weakly interacting particles such as ALPs.

Speaker: Gunjanben Akbari (Indiana University Indianapolis)

149 The First Flight of the GAPS Antarctic Balloon Experiment

The nature of dark matter remains one of the most important open questions in fundamental physics. Low-energy cosmic-ray antideuterons are a particularly compelling indirect detection channel because conventional astrophysical production is strongly suppressed at kinetic energies below approximately 1 GeV/n, making this energy range a uniquely low-background window for searches for new physics.
The General Antiparticle Spectrometer (GAPS) is the first experiment dedicated to the search for low-energy cosmic-ray antideuterons and other antinuclei. Using a novel exotic-atom technique with a large-acceptance balloon-borne instrument, GAPS is optimized for this rare-event search and provides the sensitivity and background rejection required to detect low-energy antideuterons. It also enables measurements of low-energy antiprotons and searches for antihelium. The instrument combines a plastic-scintillator time-of-flight system with a Si(Li) tracker to identify low-energy antiparticles through the formation, de-excitation, and annihilation of exotic atoms.
The first GAPS science payload was launched on 16 December 2025 and completed a 25-day Antarctic long-duration balloon flight. This talk will present an overview of GAPS and will report on the status of the first science flight, including preliminary results from flight data.

Speaker: Kazutaka Aoyama (JAXA/ISAS)

GR: GR5 : Others

150 A common four-beam geometry reveals altitude-stratified GeV pulses in canonical young pulsars

Despite the diversity and energy dependence of $\gamma$-ray pulse morphologies in Crab, Vela and Dragonfly, the phaseograms of these three canonical young pulsars can be organised within a single four-beam geometric template. Using \textit{Fermi} Large Area Telescope data, we fit the 60~MeV--3~GeV phaseograms with a mechanism-agnostic, geometry-first parametric model that incorporates phase-dependent Doppler shifts and constrains the three-dimensional locations and bulk motions of four emission sites. In each pulsar, the phaseogram admits a decomposition into two altitude-separated beam pairs. For Crab, the phaseogram alone does not uniquely require altitude separation, but co-located solutions are disfavoured when confronted with independent constraints on the viewing geometry. The lower-altitude pair is produced by plasma with bulk motion close to azimuthal corotation, sharpening the main peaks. The higher-altitude pair shows a radially outward bulk-motion component, suggestive of inertial effects in a toroidally dominated magnetic field, and contributes bridge/shoulder emission and ripple-like modulations overlapping the main peaks. The lower-altitude pair is consistent with curvature-dominated outer-magnetospheric emission, while the higher-altitude pair is consistent with synchrotron-dominated emission from a current-sheet-like outflow. Higher-altitude site heights increase from $\simeq 0.7$ (Crab, $\approx 1$~kyr) to $\simeq 1.1$--$1.4$ light-cylinder radii (Vela and Dragonfly, $\approx 10$~kyr), consistent with vertical inflation of the outflow-transition layer. This unified four-beam, observation-driven geometry maps an altitude-dependent azimuthal tilt of pulsed $\gamma$-ray emission, providing an observationally anchored framework amenable to systematic tests and readily extensible to other young pulsars.

Speaker: Paul K. H. YEUNG (ICRR, UTokyo)

151 The Butterfly Effect? An Anti-Correlation of Sunspots and High-Energy Gamma Rays

The sunspot butterfly diagram is a well known pattern, where the location of sunspots is shown to drift from higher latitudes to lower latitudes over a solar cycle, correlating with solar activity. The Fermi-LAT has been operational since 2008, collecting a full solar cycle of gamma photons from the sun over the time period of 2008-2021. We take a first look at the distribution of these high-energy gamma events and their correlation with surface features of the Sun, such as the appearance of sunspots over this time period.

Speaker: Kristy Fu (Chinese University of Hong Kong)

152 Secondary Electron-Positron Pairs as a Key Component of the Solar Disk TeV Emission

The Sun exhibits a TeV flux that significantly exceeds theoretical expectations, challenging conventional particle interaction models. In this Letter, we demonstrate that secondary electron-positron ($e^{\pm}$) pairs constitute a crucial and irreducible component of the observed solar signal. Due to their Extensive Air Shower (EAS) morphology being virtually indistinguishable from that of gamma rays in ground-based arrays, this leptonic component has been overlooked in current interpretations. By employing the \textsc{G4Solar} framework with a data-driven Outward Cosmic Ray'' (OCR) injection model, we successfully reproduce the broadband spectra measured by Fermi-LAT and HAWC. Our results show that escaping secondary $e^{\pm}$ contribute approximately 20\% of the total signal in the TeV regime, with a fraction that exhibits a 2--3$\times$ anti-correlation with the solar cycle. We propose aShadow-Center'' reference frame analysis to mitigate magnetic smearing, providing a vital diagnostic tool for future experiments like LHAASO and SWGO to identify this leptonic component.

Speaker: wenyu cao

153 Multi-Messenger Concordance for the Cygnus Region as the Source of the Cosmic-Ray Knee

The Large High Altitude Air Shower Observatory (LHAASO) has recently released the highest-energy measurements of the diffuse gamma-ray flux, offering the opportunity to study the spatial distribution and energy spectrum of Galactic cosmic rays (CRs) in the TeV-PeV sky through a multi-messenger approach. In addition, the high-precision CR observations by the same collaboration have revealed a pronounced feature in the proton spectrum at $\sim3-4$ PeV (associated to the CR 'knee'), while their observations of diffuse gamma-rays above $100$ TeV do not exhibit a corresponding spectral break. This persistent tension between the two observed components seems to challenge conventional scenarios, in which the local CR distribution is representative of the Galactic CR sea. In this work, we explore as a possible alternative, the scenario of a dominating contribution of a local PeVatron in the Cygnus region (an Ultra-High-Energy gamma-ray cocoon observed by LHAASO) to the CR 'knee'. We develop a two-population model of the Galactic CR flux, which we compare to the latest CR data available by satellite missions and ground-based observatories. We contrast the diffuse gamma-ray flux predicted from our model with recent observations and discuss the conditions of the CR populations that may alleviate the aforementioned tension. Finally, we also consider the contribution of our model to the diffuse neutrino flux and compare it with observations of the Galactic Plane by the IceCube Neutrino Observatory.
(Based on work arXiv:2603.21665)

Speaker: Luis Enrique Espinosa Castro (Gran Sasso Science Institute)

154 Delayed TeV Emission from Classical Novae

Shock interaction in classical novae occurs when a fast outflow from the white dwarf collides with slower matter ejected earlier in the outburst. These shocks radiate across the electromagnetic spectrum: from radio synchrotron, to thermal optical/UV/X-ray emission, to gamma-rays. We present a parameterized one-dimensional toy model for shock interaction in classical novae that uses multi-wavelength observations to predict gamma-ray emission and test acceleration physics. In this picture, particle acceleration occurs primarily at the reverse shock generated by the collision of the white dwarf outflow with the cool, dense shell of material released at earlier times. The maximum energy of the accelerated protons, as set by a Hillas-like argument, is proportional to the thickness of the hot post-shock region, which is in turn constrained by X-ray and optical observations. For this empirically-motivated thickness, and assuming efficient magnetic amplification near the shock, we predict maximum particle energies of order 10 GeV, consistent with observed cut-offs in the spectra of Fermi-detected classical novae around the time of the nova optical peak. However, as the shock expands to larger radii the maximum proton energy can grow to more than 10 TeV, enabling the potential detection of classical novae by atmospheric Cherenkov telescopes.

Speaker: Rebecca Diesing (Columbia University and Institute for Advanced Study)

MM: MM5 : KM3-230213A and UHE Neutrinos

155 IceCube's MeV to sub-TeV KM3-230213A Follow-up

On February 13, 2023, at 01:16:47 UTC, the KM3NeT neutrino telescope detected KM3-230213A, an ultra-high-energy neutrino event without an identified electromagnetic counterpart. Its unknown origin motivates a multi-energy follow-up to probe astrophysical scenarios capable of producing neutrinos across a broad energy range. We present a coordinated analysis with IceCube spanning MeV to sub-TeV energies, searching for time-correlated or precursor neutrino emission associated with KM3-230213A. First, we investigate thermal MeV-scale neutrino bursts using the supernova data stream. Such emission is expected from dense environments such as core-collapse supernovae, collapsars, and neutron star mergers, where neutrinos are produced via thermal processes. These signals, with typical energies of 10–30 MeV and durations from milliseconds to seconds, may precede high-energy emission and probe the central engine. Second, we perform a follow-up using the ELOWEN sample, primarily sensitive to neutrinos in the 0.5–5 GeV range. This energy regime is expected to arise from quasi-thermal processes, such as proton–neutron collisions in relativistic outflows, and provides a bridge between thermal MeV emission and higher-energy non-thermal components. Finally, we analyze the IceCube GRECO dataset, optimized for neutrinos between 10 GeV and 1 TeV, which extends the sensitivity to the higher-energy part of possible quasi-thermal emission and toward the transition to non-thermal emission. Motivated by models predicting multi-component emission, we search for time-correlated signals consistent with the direction of KM3-230213A. We will present the planned search strategy and the sensitivities of each study.

Speaker: Javier Vara

156 Results from the IceCube Follow-up of the KM3-230213A Event

On February 13, 2023, the KM3NeT collaboration observed KM3-230213A, the most energetic event observed to date, with an estimated energy of ~200 PeV. KM3NeT is a next-generation underwater neutrino telescope under construction in the Mediterranean Sea, which will eventually instrument a cubic kilometer of seawater. Understanding the origin of this event could shed light on the most extreme astrophysical acceleration mechanisms in the Universe. Located at the geographic South Pole, the IceCube Neutrino Observatory is a cubic-kilometer detector embedded in glacial ice. Although IceCube has roughly an order of magnitude more exposure in both livetime and effective area relative to KM3NeT, the highest-energy neutrino events recorded by IceCube reach energies of only ~10 PeV. At the declination of KM3-230213A, IceCube is also more sensitive than KM3NeT to neutrinos with energies from 1 TeV to 1 EeV. This work presents findings from three complementary searches using IceCube data, targeting both steady and time-dependent neutrino emission from the direction and timing of KM3-230213A using both tracks and cascades.

Speaker: Riya Shah (Kavli IPMU / UTokyo)

157 Cosmogenic Origin of KM3-230213A: Delayed Gamma-Ray Emission from A Cosmic-Ray Transient

The highest-energy cosmic neutrino detected by the ARCA detector of KM3NeT has reignited the quest to pinpoint the sources of ultrahigh-energy cosmic rays (UHECRs; $E\gtrsim 0.1$ EeV). By uncovering the associated multimessenger signals, we investigate the origin of the 220 PeV $\nu_\mu$ event KM3-230213A from an unknown transient that accelerated cosmic rays to $\sim 10$ EeV. Unlike an astrophysical origin, where the $\nu_\mu$ is produced inside the source, here we consider UHECR protons that escape the source interact with the cosmic background radiation, producing a PeV-EeV cosmogenic neutrino spectrum. The secondary $e^\pm$ and $\gamma$-rays initiate an electromagnetic cascade, resulting in a cosmogenic $\gamma$-ray spectrum. The latter peaks at a delayed time of $\gtrsim 10^4$ years compared to the light travel time from the transient to observer, due to deflection of charged particles in the extragalactic magnetic field (EGMF). Our results shed light on the nature of the UHECR source for the $\nu_\mu$ event and provide crucial insights into the detection of multi-TeV $\gamma$-rays of cosmogenic origin from similar past cosmological transients. Using the $\gamma$-ray sensitivity of currently operating and next-generation imaging atmospheric Cherenkov telescopes, the flux and time-delay distribution can constrain the source distance. We further show that the detection of such a $\gamma$-ray signal above the background depends on the EGMF strength. Together with the non-detection of coincident spatial or temporal photon counterparts at the current epoch, this detection is the first compelling candidate for a sub-EeV cosmogenic neutrino.

Speaker: Sovan Boxi (Raman Research Institute)

158 Can a gamma-ray dim radio blazar produce a 200-PeV neutrino? The case of PMN J0606 −0724 and KM3-230213A

An extremely energetic muon has been recently detected by the Cubic Kilometre Neutrino Telescope (KM3NeT), indicating the observation of a neutrino. Radio blazar PMN J0606−0724, not detected in gamma rays, is located within the reported error region of the neutrino arrival direction, and was flaring at the time of the event. Here we demonstrate that the neutrino could be produced in a photohadronic interaction in its radio core. The necessary proton power is of order of the source's photon luminosity, and protons can be accelerated to the required energies in the core, while high-energy gamma rays cannot leave the source because of intense production of electron-positron pairs. Expected contribution of the population of similar flaring sources matches non-observation of energetic events by other neutrino telescopes.

Speaker: Polina Kivokurtseva (INR RAS)

159 Cosmogenic neutrinos from the high-redshift universe

Data of the James Webb Space Telescope (JWST) has revealed a surprisingly large number of active galactic nuclei (AGN) populating the universe at large redshifts (5 < z < 10). The nature of these objects is not tightly constrained observationally yet. We discuss the cosmogenic neutrino flux arising from these sources if they are capable of accelerating cosmic ray protons to energies up to ~1e19 eV. Interactions with the high-redshift CMB result in a pronounced bump in the neutrino flux around 50 PeV, which can saturate the current estimate of the neutrino intensity from the IceCube Neutrino Observatory within the parameter space allowed by JWST observations. The non-association of neutrino events to point sources in a future high-statistics observation of the 50 PeV bump could indicate that their origin lies in the high-redshift universe.

Speaker: Maximilian Meier (Chiba University -- ICEHAP)

NU: NU4 : Low-Energy Neutrino Physics

160 RELICS: A liquid xenon time projection chamber for reactor CEvNS

Exhibiting the largest cross-section of all interaction channels for MeV neutrinos, coherent elastic neutrino-nucleus scattering (CEvNS) offers a compelling pathway for the remote monitoring of nuclear reactors. Liquid xenon time projection chambers (LXeTPCs) have emerged as an ideal technology for CEvNS detection, primarily due to their low backgrounds and energy thresholds. The RELICS (REactor neutrino LIquid xenon Coherent Scattering) experiment leverages this technology to target reactor CEvNS. RELICS is designed to perform precise measurements of the CEvNS cross-section, thereby advancing our understanding of fundamental neutrino properties and facilitating the search for physics beyond the Standard Model. This talk will introduce the status of the RELICS experiment and discuss its physics potential.

Speaker: Qing Lin (University of Science and Technology of China)

161 The search for neutrinoless double beta decay of Xe-136 with the LUX-ZEPLIN experiment

LUX-ZEPLIN (LZ) is the world-leading detector for weakly interacting massive particles (WIMPs) with masses above 5 GeV/c$^2$. Nearly a mile underground at the Sanford Underground Research Facility (SURF), LZ employs a dual-phase xenon time projection chamber with a 7-tonne active volume, augmented by a two-component anti-coincidence veto system. With over 600 kg of $^{136}$Xe in its target volume, an ultra-low background environment, and excellent energy resolution, LZ is capable of competitive searches for neutrinoless double beta decay ($0\nu\beta\beta$). Such a search probes the fundamental properties of neutrinos and demonstrates the broad scientific reach of LZ. In this talk, I will describe the challenges and benefits of performing a $0\nu\beta\beta$ search in a dark matter detector, and will report on recent efforts towards this search in LZ.

Speaker: Aiham Al Musalhi (University College London)

162 Solar Atmospheric Neutrinos: A Simulation-Based Flux Calculation with Solar Magnetic Field and Neutrino Propagation

Solar atmospheric neutrinos in TeV range are important as a background for indirect detection of WIMP annihilation in the Sun. This work presents a flux calculation (up to 100 TeV), which incorporates both the solar magnetic field and neutrino propagation effects. Neutrino production in the magnetic field is simulated using Geant4, while the propagation (with both interaction and oscillation) is handled by nuSQuIDS. Results without the solar magnetic field are benchmarked against existing literature, and the effects of the solar magnetic field on flux production are discussed.

Speaker: Ho Lung Ma (The Chinese University of Hong Kong)

163 Overview and Latest Physics Results in JUNO

The Jiangmen Underground Neutrino Observatory (JUNO) is a multi-purpose neutrino experiment in southern China, built 650 m underground and positioned 52.5 km from the Yangjiang and Taishan nuclear power plants. Its primary goals are to determine the neutrino mass ordering and measure the oscillation parameters sin²θ₁₂, Δm²₂₁, and Δm²₃₁ with unprecedented precision.

To achieve these goals, the detector features a 20-kiloton ultra-pure liquid scintillator in a 17.7-m-radius acrylic sphere, instrumented with 17,596 large (20-inch) and 25,587 small (3-inch) photomultiplier tubes, surrounded by a water pool and an external plastic scintillator top tracker for background rejection. After over a decade of construction and commissioning, JUNO began physics data taking on August 26, 2025. With just 59 days of initial data, the experiment has already delivered world-leading measurements of sin²θ₁₂ and Δm²₂₁. This talk will present a comprehensive overview of JUNO and latest physics results.

Speaker: Qishan Liu (IHEP)

164 Capturing neutrons in deep-sea neutrino telescopes

Neutron capture provides a low-energy but distinctive delayed signal that can be exploited in large-volume neutrino telescopes. At TeV–PeV energies, hadronic interactions in neutrino-induced showers produce secondary neutrons. The subsequent neutron capture signals ("neutron echo") offer a powerful tool to distinguish hadronic and electromagnetic components, enabling the separation of charged-current and neutral-current interactions and providing sensitivity to neutrino flavor composition.

Extending to lower energies, neutron capture also enables event-level detection of MeV-scale antineutrinos, such as those from the long-awaited next Galactic core-collapse supernova (CCSN). In inverse beta decay, a prompt positron is followed by a delayed neutron signal, forming a characteristic coincidence signature. In seawater, capture on naturally abundant chlorine enhances this signal through higher-energy gamma emission and shorter capture times, significantly improving detection efficiency and background rejection. In addition to simulations, we validate this approach experimentally using an AmBe neutron source with a single hDOM of TRIDENT, achieving a statistically significant neutron signal despite its lower intensity compared to that expected from a typical Galactic CCSN.

Speaker: Ruike Cao (Tsung Dao Lee Institude, SJTU)

165 Neutron invisible decay in ancient minerals

There has been a long-standing tension in measurements of the neutron lifetime between beam and bottle experiments. It has been established that such a disagreement could be explained by any additional decay channel that does not involve protons in the final state. We present a search using ancient minerals to look for invisible neutron decay, a.k.a. paleodetection. If neutrons in minerals decay via such a channel, the recoiling nuclei would create tracks a few microns in length. Since these tracks are well above typical readout resolution, it is feasible to scan of order 100 grams of sample, giving a total exposure of order 100 kiloton-years. This makes paleodetection a promising a complementary probe of the neutron lifetime anomaly.

Speaker: Ms Audrey Fung (APCTP)

3:30 PM break

CR: CR5 : Magnetic Field

166 Intergalactic magnetic field lower limits up to the redshift $z\approx3$

Large-scale intergalactic magnetic fields (IGMFs) may comprise both galactic and cosmogenic components, which can be probed via observations of delayed $\gamma$-ray emission from electromagnetic cascades initiated by the highest-energy photons emitted by distant sources. These components can, in principle, be distinguished through their redshift evolution; however, observational evidence for non-negligible magnetic fields has so far been largely limited to low redshifts.

This work extends constraints on the IGMF to redshifts $z \gtrsim 1$ using 17 years of all-sky observations of high-redshift active galactic nuclei with the Fermi/LAT $\gamma$-ray telescope. By combining Fermi/LAT data in the 0.1 GeV – 1 TeV energy range with Monte Carlo simulations of $\gamma$-ray-induced electromagnetic cascades, it is shown that the null hypothesis of zero magnetic field strength in the redshift interval $z \in [0.5,\,3]$ is disfavoured at the $\approx 8.6\sigma$ significance level. This corresponds to a lower bound of $B \gtrsim 1 \times 10^{-18}$ cG for magnetic field correlation lengths exceeding 1 Mpc.

The same dataset further constrains the volume-filling fraction of the IGMF to $f \gtrsim 90\%$ within the probed redshift range. The robustness of these results is verified against potential systematic effects, including source flux variability and uncertainties in the $\gamma$-ray attenuation model.

These results provide the first evidence to date for pervasive intergalactic magnetic fields at $z \gtrsim 1$, placing new constraints on their origin and evolution.

Speaker: Ievgen Vovk (ICRR, The University of Tokyo)

167 Constraining the Intergalactic Magnetic Field with Time-Delay Likelihoods in Gamma-Ray Transients

A cosmological origin of magnetic fields in large-scale structures implies the existence of a weak intergalactic magnetic field (IGMF) in cosmic voids, which remains undetected. High-energy gamma rays from distant transients, provide an indirect probe: during propagation, TeV γ-rays initiate electromagnetic cascades whose charged components are deflected by the IGMF, producing a characteristic time-delayed emission at GeV energies.

The most stringent lower limits to date, derived from gamma-ray bursts (GRBs) observed with the Fermi-LAT, reach B ≳ 10⁻¹⁷ G, but depend on assumptions about the intrinsic temporal behaviour of the source emission.

In this work, we introduce a novel binned likelihood framework to analyse time delays in gamma-ray light curves, removing the need for assumptions on the intrinsic variability of the source. This approach enables a more robust and conservative determination of IGMF constraints.

We apply this method to simulated and observed light curves of transient sources, including GRBs and active galactic nuclei (AGN) flares, across a range of redshifts, in the context of observations with the Cherenkov Telescope Array Observatory, in particular its Large-Sized Telescopes (LSTs). Leveraging its unprecedented sensitivity at very high energies, our approach allows us to constrain the IGMF strength within the range B ~ 10⁻²⁰ - 10⁻¹⁶ G under minimal assumptions, significantly improving upon current limits.

Speaker: Mathilde Croisonnier

168 Reading the Universe’s Light: Measuring the Extragalactic Background Light Through Gamma-Ray Attenuation

The extragalactic background light (EBL) encodes the integrated emission history of all extragalactic sources and serves as a key probe of star formation and galaxy evolution. Gamma-ray observations offer a unique method to measure the EBL through the energy-dependent attenuation of blazar spectra via pair production with EBL photons. We present complementary EBL measurements spanning GeV to TeV energies. Using 15 years of Fermi-LAT data and 1576 blazars, we detect EBL attenuation at ~23 sigma significance and measure the optical depth across 19 redshift bins out to z ~ 4.3, providing the most precise GeV determination of the EBL to date. At very high energies, we analyze 268 spectra from 45 sources observed with Imaging Atmospheric Cherenkov Telescopes, finding that seven EBL templates require only ≤10% rescaling to match the observed attenuation. Combining GeV and TeV optical depths, we reconstruct the local EBL intensity at z = 0 using both empirical and physically motivated models. The reconstructions agree with integrated galaxy counts to within 2-3 nW m⁻² sr⁻¹ over 0.5-30 μm, while the near-IR excess reported by IRTS and CIBER is disfavored at 3-5 sigma. These results indicate that known galaxy populations account for most of the optical-to-near-IR background.

Speaker: Dr Joshua Baxter (Clemson University)

169 Globular Cluster Systems as GeV-TeV Tracers of Galaxy Assembly

Globular clusters (GCs) are long-lived relics of galaxy assembly and retain important information about merger history, chemical enrichment, and the build-up of galactic bulges and halos. We investigate the prospect that their high-energy emission may provide a new, complementary way to probe this evolution. In our scenario, millisecond pulsars (MSPs) in GCs power persistent GeV emission, while electrons re-accelerated in communal stellar/pulsar-wind termination shocks generate TeV gamma-rays through inverse-Compton scattering as they propagate into GC magnetotails. We model the integrated GeV–TeV output from GC systems embedded in galaxies with different evolutionary pathways, including quiescent growth, minor-merger-driven assembly, and major mergers or strong interactions. The predicted gamma-ray signal depends on the total GC population, and its radial and metallicity distribution. Centrally concentrated, metal-rich GC populations formed in major mergers can produce prominent GeV and TeV signatures, whereas GC systems built mainly through minor accretion are expected to be GeV-bright but comparatively TeV-faint because many clusters reside in lower-density outer halos. Quiescent systems show much weaker GC-related high-energy emission. These results suggest that gamma-rays can provide a novel probe of GC populations and, through them, of galaxy evolution itself. Moreover, they offer the advantage of being able to bypass dust obscuration in dense inner galactic regions where conventional tracers of GC systems are often incomplete. This opens a new route for connecting TeV observations of nearby galaxies to their fossil assembly histories.

Speaker: Ellis Owen (RIKEN)

170 Coronal Magnetic Field Modulates Giga-electronvolt Solar Disk Gamma Rays

Solar disk gamma rays, theorized to originate from hadronic galactic cosmic ray interactions, exhibit many puzzling features. Above 0.1 giga-electronvolts (GeV), these features include high flux and anti-correlation with the solar activity cycle. Between 10 and 50 GeV, it also displays an unexpected time- and energy- dependent morphology. A key question is how solar magnetic fields could affect solar disk gamma rays. The magnetic field in solar corona, in particular, is complex in structure, variable in time, and difficult to probe. Here we present the first model of time-dependent gamma-ray flux across an entire solar cycle, produced using simulation toolkit G4SOLAR and incorporating state-of-the-art coronal magnetic field models. Our result produces good agreement with observations in both flux and time variation between 0.1 and 1 GeV, showing the open coronal fields as the dominant cause. We further predict distinct morphological signatures linked to coronal magnetic field structures, which can be verified by future gamma-ray telescopes. These findings establish a clear connection between coronal field and GeV gamma-ray emission, positioning solar gamma rays as a novel tool to study solar physics.

Speaker: Chingam Fong (The Chinese University of Hong Kong)

171 Simulation of Earth-Limb Gamma-Ray Intensity Dependence on Geomagnetic Cutoff Rigidity

We present a simulation study of Earth albedo gamma-ray intensity as observed by the Fermi Large Area Telescope (LAT), and its dependence on geomagnetic cutoff rigidity of cosmic ray proton. We perform Monte Carlo simulations of particle interactions in the Earth’s atmosphere using GEANT4, including the effects of the geomagnetic field. Our simulation result confirm the correlation, previously reported in Fermi LAT observations, between the Earth’s limb gamma-ray intensity and the geomagnetic cutoff rigidity of primary cosmic ray protons. This work is relevant for studies of geomagnetic field and for near-Earth spacecraft missions.

Speaker: Yu On Xu (The Chinese University of Hong Kong)

172 Measuring the Cosmic Ray Sun and Moon Shadow with IceCube*

On their way to Earth, cosmic rays are blocked by the Sun and Moon, leading to a relative deficit of detectable cosmic rays at Earth, the cosmic ray Sun/Moon shadow. With the IceCube Neutrino Observatory, atmospheric muons are detected that are produced when cosmic rays interact with the Earth’s atmosphere. While the Moon shadow serves as an absolute pointing calibration, the Sun shadow depth and shape depend on the details of the solar magnetic field strength and structure. The turbulent and large-scale fields deflect the charged cosmic rays and thus leave their footprint in the Sun shadow. We present an event selection and method for measuring the Sun and Moon shadows with IceCube. We discuss how these observations help to enhance our understanding of the solar magnetic field. *Supported by BMFTR

Speaker: Niclas Krieger

173 Radial velocity statistics of cosmic voids as a probe of interacting dark energy

Due to their size and underdense structures, cosmic voids offer enhanced sensitivity to the properties of dark energy. We show that the Type 3 interacting dark energy model parameters have significant effects on the radial velocity and velocity dispersion of these voids, though the effects of the momentum coupling $\beta$ ($<0$ ) and scalar field potential parameter $\lambda$ on the radial velocity statistics are degenerate, similar to that previously reported for matter pairwise velocities in the same model. This demonstrates that the void velocity profiles provide an independent and observationally accessible probe of the dark-sector interaction in the Type 3 model. We show that the degeneracy between $\beta$ and $\lambda$ can be broken when the void velocity statistics are combined with matter pairwise velocity statistics.

Speaker: Kin Ho Luo (The Chinese University of Hong Kong)

DM: DM6 : Direct Detection and Light/Boosted Dark Matter

174 The XENONnT experiment and its latest results

The XENONnT experiment is a direct dark matter search experiment using a time projection chamber filled with 8.5 tonnes of liquid xenon, operated at Laboratori Nazionali del Gran Sasso (LNGS), Italy. The detector collected science data since 2021 to 2025, and is currently undergoing upgrade to further improve the sensitivity.
In this talk, I will present an overview of the experiment, along with the latest physics results and the current status of the detector upgrade.

Speaker: Masatoshi Kobayashi (Nagoya University)

175 Boosted electron-coupling dark matter search with the LUX-ZEPLIN (LZ) experiment

The LZ experiment is a dual-phase xenon time projection chamber for direct dark matter searches located in Lead, South Dakota, USA. Although LZ’s primary goal is the direct detection of weakly interacting massive particles (WIMPs) via low-energy nuclear recoils, it can also leverage its low background to search for alternative beyond standard model physics scenarios , including dark matter coupling to electrons. Such dark matter is challenging to detect in xenon detectors because the expected electronic-recoil signals often fall below the detector’s energy threshold. However, astrophysical high-energy electron populations can boost dark matter into the observable energy range of LZ. In this talk, I will present an LZ search for such signals based on a 4.2 tonne-year exposure. I will discuss the analysis strategy, and show results for several source scenarios, including cosmic rays, active galactic nuclei, primordial black hole evaporation, and solar thermal processes.

Speaker: Yongheng Xu (Universitetet i Oslo)

176 Boosted Dark Matter Directionality in Large Liquid Scintillator Detector

We demonstrate the differences, with and without directionality information from knockout neutrons, on the sensitivities of Jiangmen Underground Neutrino Observatory JUNO on dark matter (DM) direct detection. Sub-GeV DM can be boosted by cosmic rays to leave a detectable signal in liquid scintillator detectors. These boosted dark matter (BDM) are dominated around the galactic center due to DM density profile. As BDM undergoes quasi-elastic scattering with carbon and knocks out a neutron, we show, using Geant4, that these neutrons retain partial directional information of the initial BDM after diffusion. For directional information, we targeted two interaction vertices involve tracing a gamma ray from nuclear de-excitation, together with a time-delayed gamma ray from neutron capture. At last, we conclude the directionality information mildly improves the spin-independent DM–nucleon scattering cross-section constraint because the BDM-induced neutron sky map lacks contrast.

Speaker: Samuel S. H. Tse (The Chinese University of Hong Kong)

177 Light Dark Matter Detection at Torsion Balance

Light dark matter with sub-eV masses has a high number density in our galaxy, and its scattering cross section with macroscopic objects can be significantly enhanced by coherence effects. Repeated scattering with a target object can induce a measurable acceleration. Torsion balance experiments with geometric asymmetry are, in principle, capable of detecting such signals. Our analysis shows that existing torsion balances designed to test the Equivalence Principle already place the most stringent constraints on DM-nucleon scattering in the $(10^{-2}, 1)\,$eV mass range.

Speaker: Jie Sheng (Kavli IPMU)

178 Solar Dark Matter below the Evaporation Limit: A Monte Carlo Study

Abstract

The Sun provides a complementary probe of sub-GeV dark matter (DM) through spin-dependent DM–proton scattering and neutrinos from DM annihilation. For $m_\chi \lesssim 4\ \mathrm{GeV}$, where evaporation is significant, the spatial distribution of the captured DM population is a key uncertainty in predicting the annihilation rate and neutrino flux. We use DaMaSCUS-SUN to perform Monte Carlo trajectory simulations for $m_\chi = 0.1–4\ \mathrm{GeV}$, following DM capture, scattering, thermalization and evaporation without assuming an equilibrium density profile or Knudsen interpolation. We find systematic, order-unity deviations from the conventional Knudsen-interpolated density profile in the optically thin, evaporation-dominated regime. These deviations are driven primarily by evaporation, while incomplete thermalization plays a secondary role by leaving a residual fraction of DM on extended, non-thermal orbits. Our results provide a direct simulation-based test of the assumptions underlying current solar DM limits below 4 GeV and have implications for the robustness of neutrino-based constraints in this mass range.

Speaker: Lingyu Xia (The Chinese University of Hong Kong)

179 New physics searches at the NA62 experiment

Searches for the decays $K^{+}\rightarrow\pi^{+}X$ and $\pi^{+}\rightarrow e^{+}N$ are presented using data collected by the NA62 experiment at CERN in 2016--2022 and 2017--2024, respectively. Results are interpreted to constrain a range of new physics scenarios covering all four portal model scenarios. Upper limits on the $K^{+}\rightarrow\pi^{+}X$ branching ratio are established at the $10^{-11}$ level, providing constraints on dark photon, scalar and ALP couplings. From the search for heavy neutral lepton production in $\pi^{+}\to e^+N$ decays of beam pions, upper limits of the extended neutrino mixing matrix element $|U_{e4}|^2$ are established at the $10^{-8}$ level over the heavy neutral lepton mass range 95--126~MeV/$c^2$. The NA62 experiment has the capability to collect data in a beam-dump mode, where 400~GeV protons are dumped on an absorber. In this configuration, new physics particles may be produced in the absorber and decay in an instrumented volume beginning approximately 80 m downstream of the dump. Preliminary results from a search for heavy neutral leptons decaying in flight to semi-leptonic final states are reported, based on an analysis of a sample of $6.2 \times 10^{17}$ protons on dump collected by NA62 in 2021, 2023, and 2024.

Speaker: Xiafei Chang

GR: GR6 : Instruments

180 Status Report of ALPACA: a new air shower array experiment for ultra-high-energy gamma-ray astronomy in the southern hemisphere

Andes Large-area PArticle detector for Cosmic-ray physics and Astronomy (ALPACA) is an air shower array experiment that aims to observe ultra-high-energy (UHE) gamma rays in the southern sky in 2027. It consists of a surface air shower array with a geometrical area of 83,000 ${\rm m}^2$ and a water Cherenkov-type muon detector array with a 2.0 ${\rm m}$ soil overburden covering an area of 3,600 ${\rm m}^2$. The prototype experiment called ALPAQUITA, a surface air shower array with an area of 18,000 ${\rm m}^2$, has been stably taking data since April 2023. The ALPAQUITA data is now being analyzed to validate the performance of the experiment and to study physics, such as the measurement of the cosmic-ray spectrum and the Forbush decrease due to large solar flares. Moreover, the muon detectors are under construction since November 2025; an extended prototype array equipped with a muon detector of a 900 ${\rm m}^2$ area will start the observation sensitive to UHE gamma rays in 2026. The presentation will detail the concept of our experiment, the current situation of the detector construction, and some results of the data analysis using the prototype experiment.

Speaker: Sei Kato (Kyoto University)

181 Optimization of gamma-ray energy reconstruction in ALPAQUITA

In Andes Large-area PArticle detector for Cosmic-ray physics and Astronomy (ALPACA), an air-shower array designed for sub-PeV $\gamma$-ray observations in the Southern Hemisphere, the accuracy of primary energy reconstruction is a key factor that determines the energy spectrum of individual $\gamma$-ray sources.

In this study, we compare the performance of $\gamma$-ray energy estimators based on the lateral density parameter $S_{x}$, where $x$ is the shower core distance to be optimized, and the sum of particle densities, $\Sigma \rho$, using Monte Carlo simulations. By constructing energy conversion functions that take the zenith-angle dependence into account, we evaluate the energy resolution and bias from the distribution of $\ln(E_{\mathrm{rec}}/E_{\mathrm{true}})$.

We find that among the tested estimators, the lateral density parameter at 40 m ($S_{40}$) provides the best energy resolution. Within the $S_{x}$ family, $S_{40}$ outperforms larger core distances such as $S_{70}$; for example, in the 30--100 TeV range, the resolution improves from about 39% to 30%, corresponding to an improvement of about 5--10%. Compared to the sum of particle densities, $\Sigma \rho$, $S_{40}$ further improves the energy resolution from about 30% to 20%.

In this presentation, we discuss the details of each energy estimator and their performance. We will also discuss their impact on the determination of the $\gamma$-ray energy spectrum.

Speaker: Yuji Yamanaka (Institute for Cosmic Ray Research, University of Tokyo)

182 Improving Air Shower Reconstruction in HAWC Using the Outrigger Array

The High Altitude Water Cherenkov (HAWC) observatory is a wide-field gamma-ray detector located at an altitude of 4100 m in Mexico, sensitive to gamma rays in the energy range from 300 GeV to several hundred TeV. HAWC consists of 300 water Cherenkov detectors (WCDs) in the main array and 345 smaller WCDs in the surrounding outrigger array. The current air shower reconstruction uses only the main array, while including data from the outrigger array can improve reconstruction performance at the highest energies.

In this work, we evaluate the impact of the outrigger array on air shower reconstruction using Geant4-based detector simulations and the HAWC reconstruction algorithm. We compare the instrument response functions (IRFs) obtained with and without outrigger signals, including angular resolution, core resolution, energy resolution, effective area, gamma/hadron separation, and expected sensitivity to gamma-ray sources.

Speaker: Junho Gyeong (Sungkyunkwan University (SKKU))

183 Enhancing Muon Identification in the SWGO Outer Array with MultiPMT Modules through Machine Learning Techniques

Water Cherenkov Detectors play a central role in high-energy astroparticle physics, with key applications in neutrino physics, gamma-ray astronomy, and cosmic-ray research. The performance of these detectors crucially relies on photomultiplier tubes (PMTs) to capture Cherenkov radiation. In recent years, employing multiPMT modules has emerged as a promising strategy to enhance the capabilities of large volume water and ice Cherenkov detectors.

In this presentation we will explore the innovative use of multiPMT modules integrated into small Water Cherenkov Detector units as a possible configuration for the outer array of the Southern Wide-Field Gamma-Ray Observatory (SWGO), a next generation experiment for high energy gamma ray detection based on an array of Water Cherenkov Detector units. SWGO will be located in the Atacama Desert in Chile and will be dedicated to gamma-ray surveys of the southern sky, covering an energy range from hundreds of GeV up to a few PeV.
The performance of gamma-ray experiments strongly depends on effective rejection of the hadronic background which can be achieved by successfully identifying the muonic component of the showers among other shower properties. We will investigate the potential of multiPMT modules by exploiting their intrinsic sensitivity to the directionality of Cherenkov light, training a machine-learning model capable of identifying the distinct spatial features of emission from muons and from the electromagnetic component of extensive air showers. We will then discuss the effectiveness of this strategy for muon counting and muon tagging in gamma–hadron discrimination studies.

Speaker: Vincenzo Maria Grieco (Scuola Superiore Meridionale)

184 Probing the PeV Gamma-Ray Sky with PEPS

The Probing Extreme PeVatron Sources (PEPS) project is designed to explore the largely uncharted energy range between $10^{15}$ eV and $5 \times 10^{16}$ eV in gamma rays. PEPS will search for the most extreme Galactic accelerators, probe super-heavy dark matter scenarios, and investigate the transition from Galactic to extragalactic cosmic rays. The experiment will be deployed at the site of the Pierre Auger Observatory, taking advantage of its infrastructure and excellent view of the Galactic Plane and the Galactic Center. The detector concept is based on two-layer water-Cherenkov stations, enabling a suppression of the cosmic-ray background by more than three orders of magnitude at PeV energies with a gamma-ray efficiency of about 50%. The initial $2\ \mathrm{km}^2$ array will already represent the largest detector in this energy range. Prototype detectors operated at the Pierre Auger Observatory over the past decade have demonstrated the robustness of the design. A new prototype is planned in Japan to further optimize the detector and strengthen international collaboration. In this contribution, we present the current status of PEPS, its expected performance, and its scientific potential in the context of PeV gamma-ray observations.

Speaker: Eiji Kido (Institute for Cosmic Ray Research, University of Tokyo)

185 First Light with the Prototype Schwarzschild-Couder Telescope's Upgraded Camera

The Cherenkov Telescope Array Observatory (CTAO) is an upcoming very-high-energy gamma-ray observatory which will have an order of magnitude better sensitivity than the current generation of imaging atmospheric Cherenkov telescope arrays. The Schwarzschild-Couder Telescope is a candidate design for a CTAO medium-sized telescope featuring a finely pixelated camera populated with silicon photomultipliers (SiPMs) and innovative dual-mirror optics. The prototype Schwarzschild-Couder Telescope (pSCT) was inaugurated in 2019 at the Fred Lawrence Whipple Observatory in Arizona and detected the Crab Nebula with a partially populated focal plane. The pSCT camera is currently undergoing an upgrade to fully instrument the 8.04° diameter field-of-view (FoV) with 11,328 SiPM pixels. The upgraded camera modules feature design changes to reduce electronics noise and crosstalk. These changes will improve the telescope's low-energy performance and background rejection capabilities. The first sector of 1,408 pixels was installed in April of 2026. We will present first light with this sector of the pSCT camera upgrade, as well as early commissioning data.

Speaker: Zachary Curtis-Ginsberg (University of Wisconsin - Madison)

MM: MM6 : Time-Domain Multimessenger Studies

186 Real-time astronomy with KM3NeT

Modern astronomy relies on the combined observation of the Universe through multiple messengers, including electromagnetic radiation, cosmic rays, gravitational waves, and neutrinos. Time correlation across these channels is essential for the discovery and characterisation of transient astrophysical sources, as well as for probing the mechanisms driving the most extreme cosmic phenomena. These objectives demand low-latency infrastructures capable of reacting promptly to external alerts and disseminating significant detections to the global multi-messenger community.
KM3NeT, a large-scale neutrino observatory under construction in the Mediterranean Sea, is already operating with partial detector configurations. It consists of two complementary deep-sea Cherenkov detectors: ARCA, targeting neutrinos in the TeV-PeV energy range, and ORCA, optimised for GeV-TeV neutrinos. In addition, both detectors are sensitive to the collective MeV neutrino emission from core-collapse supernovae. This combination provides near-continuous sky coverage and enables the monitoring of transient phenomena over a wide range of energies.
To support global multi-messenger observations, the KM3NeT Collaboration has developed a dedicated real-time analysis framework. Events are reconstructed and classified with minimal latency, allowing the rapid selection of promising neutrino candidates. The system performs continuous follow-up of external alerts from other observatories and experiments, searching for temporal and directional coincidences. In parallel, a real-time alert-sending pipeline is being deployed to automatically assess the significance of detected events and promptly issue alerts to partner facilities. Currently in an advanced commissioning phase, this alert system marks an important milestone in KM3NeT's integration into the global network of real-time multi-messenger observatories.

Speaker: Martina Marconi (INFN Genova - Università di Genova)

187 IceCube Realtime Program: Connecting high-energy neutrinos to the multi-messenger sky

Since 2016, the IceCube Neutrino Observatory has operated a real-time alert system to identify high-energy neutrino events and promptly notify the astronomical community for electromagnetic and gravitational-wave follow-up. A major success of the program was the detection, a year later, of a high-energy neutrino from the blazar TXS 0506+056, demonstrating the power of rapid multi-messenger observations. In this talk, I will give an overview of the IceCube realtime program, including all alert types and follow-up strategies, with a focus on track-like events. In September 2024, improvements in event reconstruction significantly enhanced the angular resolution of track alerts and improved sensitivity and coverage. In particular, the 50%(90%) angular uncertainty on tracks has been reduced by a factor of ~5(~4). In this talk, I will discuss the updated system performance and outline prospects for future astrophysical neutrino discoveries in the era of multi-messenger astronomy.

Speaker: Angela Zegarelli (Ruhr University Bochum)

188 Time-dependent neutrino search during gamma ray flares with the ANTARES and KM3NeT and neutrino telescopes

The correlation between gamma-ray and neutrino emissions due to hadronic processes in astrophysical sources is of special interest for multi-messenger astronomy as both channels of detection offer complementary information about the sources studied.

The ANTARES neutrino telescope was a 0.01 $km^{3}$ volume detector located at the bottom of the Mediterranean Sea. It operated from 2007 until early 2022, and over its span it accumulated valuable neutrino data; KM3NeT/ARCA is located 100 km offshore Portopalo di Capo Passero in Sicily at a depth of 3.5 km, and is an undersea neutrino telescope dedicated to high-energy neutrino studies (up to multi-PeV). It will have a volume of $1 km^{3}$ upon completion. Both detectors work on the cherenkov light detection principle and their combination provides more than 16 years of cosmic neutrino data with excellent angular resolution, thanks to the optical properties of the deep Mediterranean Sea. On the other hand, gamma ray telescopes such as Fermi-LAT offer continuous and precise information of the gamma ray emission of cosmic neutrino source candidates, such as blazars.

The analysis presented in this contribution uses the data from Fermi-LAT to characterize the gamma ray flare emission of variable blazars in order to search for cosmic neutrinos during these periods of emission in the combined data sets of ANTARES and KM3NeT/ARCA. This work extends previous analyses based solely on partial ANTARES data and represents a step forward in joint neutrino telescope analyses.

Speaker: Ricardo Jaimes (Universidad de Valencia-IFIC)

189 IceCube Search for Neutrinos from Thousands of Fast Radio Bursts

Fast radio bursts (FRBs) are an extremely luminous class of very short (millisecond-duration) bursts of radio waves, which are mostly extragalactic. Despite radio telescopes such as the Canadian Hydrogen Intensity Mapping Experiment (CHIME) detecting thousands of FRBs, their origins and production mechanisms are largely unknown. Their only known source association is with an X-ray flare from the Galactic magnetar SGR 1935+2154. Beyond this, many models have been proposed for the production of FRBs by various source classes, including not only pulsars but also cataclysmic phenomena such as compact object mergers. Searching for neutrinos associated with FRBs can help constrain their production mechanism. Namely, the detection of neutrinos would be strong evidence for hadronic processes. I will present IceCube’s most recent search for neutrinos from FRBs, based on CHIME/FRB Catalog 2. This analysis is the largest search to date for neutrinos from FRBs, by more than two orders of magnitude in the number of bursts searched.

Speaker: Alicia Mand (University of Wisconsin - Madison)

190 Optical Counterpart search for a Month-timescale IceCube Neutrino Multiplet Event

Optical transients with timescales of months, such as supernovae (SNe) and tidal disruption events (TDEs), are candidate sources of high-energy neutrinos. Multiple neutrino detections from the same direction on a timescale of about a month provide a unique opportunity to identify such optical counterparts in the nearby Universe. In this work, we conduct an archival search for the optical counterpart of an IceCube triplet event using data from the Zwicky Transient Facility. We develop a dedicated alert filtering system and validate its performance through a blind analysis. Applying this filtering system to the data after the detection of the IceCube triplet event, we find no transient candidates within the localization area. Assuming that the IceCube triplet event originates from an astrophysical source, we constrain the peak luminosity and decay timescale of the optical transient using a simple signal model motivated by TDEs and superluminous SNe (SLSNe). To place constraints on transients with rapidly evolving light curves, prompt follow-up observations for future neutrino multiplet events are crucial. We also discuss a follow-up strategy for upcoming real-time IceCube multiplet alerts.

Speaker: Seiji Toshikage (Tohoku University)

191 GeV Neutrino Transient Search with IceCube Upgrade

A wide variety of transient phenomena, including gamma-ray bursts, supernovae, and novae, are expected to emit GeV neutrinos. Detecting these neutrinos provides unique insights into their emission mechanisms and particle acceleration processes. IceCube Upgrade, the densest infill array in IceCube Neutrino Observatory, features newly developed multi-PMT optical modules with close spacing. It was deployed in 2026 and is currently under commissioning. IceCube Upgrade is expected to provide a significant improvement in sensitivity for transient searches in the GeV energy range. In this contribution, we present the performance of our event selection targeting GeV neutrino transients, as well as prospects for the analysis of initial data from IceCube Upgrade.

Speaker: Yukiho Kobayashi (ICEHAP, Chiba University)

192 Gamma-ray counterparts of the Fast X-ray Transients detected by Einstein Probe

The Einstein Probe mission is rapidly increasing the number of known fast X-ray transients (FXTs), opening a new window on short-lived high-energy phenomena in the Universe. A major open question is whether these FXTs represent the softer and lower-luminosity extension of the classical long gamma-ray burst (GRB) population, or whether they include events belonging to a physically distinct class of transients.

With the growing sample of Einstein Probe detections, systematic comparisons with previously known GRB populations are now becoming possible. In this work, I present a search for MeV and GeV counterparts to FXTs, aimed at assessing whether a significant fraction of these events produces detectable high-energy emission and how this emission relates to their X-ray properties. In particular, I use Fermi-GBM data to search for prompt gamma-ray counterparts, and Fermi-LAT data to place upper limits in cases with no significant detection.

These constraints also provide a way to investigate the broad-band emission of FXTs within synchrotron and synchrotron self-Compton (SSC) frameworks. If some of these transients are powered by relativistic jets, a non-detection in the LAT band may either indicate the absence of the inverse Compton or the inverse-Compton component instead peaks at higher energies, potentially in the TeV band. FXTs may therefore represent promising systems for studying the connection between X-ray transients and very-high-energy gamma-ray emission.

Speaker: Ansh Chopra (Gran Sasso Science Institute)

NU: NU5 : Neutrino Observatories

193 The Payload for Ultrahigh Energy Observations (PUEO): 2025-2026 Flight and Experiment Overview

The Payload for Ultrahigh Energy Observations (PUEO) is a long-duration balloon experiment designed to search for the astrophysical and cosmogenic neutrino flux at ultrahigh energies (>1 EeV) with world-leading sensitivity. During its successful 23-day Antarctic flight in the 2025-2026 austral summer, PUEO monitored the Antarctic ice sheet for impulsive radio signals characteristic of Askaryan radiation from ultrahigh energy neutrinos interacting in the ice. It was also sensitive to geomagnetic emission of air showers induced by ultrahigh energy cosmic rays and neutrino-produced tau decays. This talk will give an overview of PUEO’s design, flight, and ongoing calibration and analysis.

Speaker: Dr Lucas Beaufore (The Ohio State University)

194 Status and Science of the Radio Neutrino Observatory in Greenland

Ultra-high-energy neutrinos offer a unique window on the most violent phenomena in the Universe. Produced at astrophysical sources or during cosmic-ray propagation, these unattenuated and unscattered cosmic messengers probe environments inaccessible to other particles. They enable the study of their production sites, may reveal the sources of ultra-high-energy cosmic rays, and help constrain their mass composition. Their extremely low flux requires the instrumentation of vast volumes of transparent media for detection.

Radio detection via the Askaryan effect has emerged as a promising and cost-effective approach to instrument large volumes of ice with sparse arrays reaching the required sensitivities.

The Radio Neutrino Observatory in Greenland (RNO-G) is a third-generation radio neutrino array currently under construction at Summit Station. Stations have been deployed and operating for the past five years, delivering already science results. RNO-G is planned to have 35 hybrid stations in total, each capable of detecting neutrino-induced signals, reconstructing event properties, and rejecting cosmic-ray backgrounds.
In this contribution, I will present the current status of construction, commissioning, and calibration, as well as the first scientific results obtained with data from the deployed stations.

Speaker: Simona Toscano (IIHE - ULB)

195 The Radio Neutrino Observatory in Greenland (RNO-G): Simulation Progress towards a Diffuse Neutrino Search

The Radio Neutrino Observatory in Greenland (RNO-G) is an in-ice antenna array with 35 planned stations, designed to detect ultra-high-energy (UHE) neutrinos interacting in the ice in Greenland. RNO-G is designed to detect the radio signal from Askaryan radiation produced by UHE neutrinos (either astrophysical or cosmogenic in origin) when they interact in the ice sheet. Neutrinos are excellent messenger particles that can tell us about the highest-energy sources in the universe, as they only interact weakly and are not deflected as they propagate.
Each independent RNO-G station includes 24 antennas, deployed both at the surface of the ice sheet and at depths down to 100m. The first stations were deployed in 2021, and today RNO-G has a total of 8 stations in operation with an accumulated 5 years of physics data. With collaboration progress on various calibration and development efforts, we now have enough data and tools to begin searching our dataset for neutrinos.
This contribution describes simulation progress and strategy for a future neutrino diffuse search using RNO-G data from 2021-2024 by various tools developed in NuRadioMC. This includes the configuration classification of stations within the data period, important simulation tuning to match instrument performance, uncertainty estimations, and the feasibility of a multi-station simulation that matches detector performance.

Speaker: Youwei Liu (The Ohio state University)

196 Status of the Radar Echo Telescope Experiment

The Radar Echo Telescope (RET) experiment aims to probe the >PeV cosmic neutrino flux with radar, targeting ionisation trails left in the wake of in-ice neutrino-induced cascades. The current focus of the RET collaboration is the Radar Echo Telescope for Cosmic Rays (RET-CR), a pathfinder experiment that utilised secondary in-ice particle cascades - produced by high-energy cosmic ray air showers impinging on an elevated ice sheet - as a test beam for the radar method. A successful detection of in-ice cosmic ray cascades will demonstrate the feasibility of the method in-situ, allowing it to be applied towards the detection of ultrahigh energy cosmic neutrinos with the future RET-N neutrino telescope. We discuss the radar detection method and present our latest results, focusing on first data from the RET-CR pathfinder and expected signal features.

Speaker: Isha Loudon (Université Libre de Bruxelles)

197 Explaining Signal Properties in Context of Reconstruction methods for the Radar Echo Telescope for Neutrinos

The Radar Echo Telescope for Neutrinos (RET-N) is a future neutrino experiment that aims to observe the cosmic neutrino flux at the highest energies ($> 10^{16}$ eV) utilising radar. Radar allows for determining the position, speed and direction of any radio-reflecting object. High-energy neutrino interactions in glacial ice induce a particle cascade of energetic secondary particles, which in turn create a dense trail of free ionisation electrons. This trail can serve as a short-lived macroscopic radar target for neutrino detection. Therefore, radar is a potential cost-effective radio-based approach for detecting these highly energetic cosmic particles. In this work, we discuss the rich signal properties of the expected radar return from neutrino interactions in ice and how the resulting global description of these features can help develop reconstruction methods and detector design for RET-N.

Speaker: Jannes Loonen (Vrije Universiteit Brussel)

198 The Trinity Neutrino Observatory: Probing the PeV–EeV Neutrino Sky

The Trinity Neutrino Observatory is designed to detect tau neutrinos in the 1 PeV–10 EeV range by observing Cherenkov emission from extensive air showers following the decay of a tau emerging from the Earth. By bridging the gap between water/ice optical Cherenkov detectors and radio-based experiments, Trinity probes the poorly explored transition region between astrophysical and cosmogenic neutrinos.

The first phase of the project, the Trinity Demonstrator at Frisco Peak in Utah, was commissioned in 2024 and has since performed regular observations. Analysis results from more than one year of observations are presented here. These results characterize the instrument's performance and validate the path towards Trinity One, the first full-scale telescope.

With an effective collection area 16 times larger than that of the demonstrator, Trinity One will already achieve competitive sensitivities. Its azimuthal rotation capability will enable point-source searches over half of the sky, as well as follow ups of transient multi-messenger events. Updated performance projections are presented, and detection prospects are evaluated across a range of source classes.

Speaker: David Raudales (Georgia Institute of Technology)

199 Trinity's sensitivity to UHE Tau Neutrinos from X-ray Bright and Obscured AGN

To maximise the Trinity Observatory’s discovery potential for PeV-EeV tau neutrinos, identifying prime multi-messenger point sources is critical. X-ray bright and Compton-thick obscured AGN are compelling candidates; their dense environments drive efficient photohadronic neutrino production while attenuating gamma rays via pair production, making X-ray emission a vital diagnostic.

In this contribution, we explore Trinity’s sensitivity to transient ultra-high-energy tau neutrinos from diverse X-ray bright AGN. We outline a framework translating observed X-ray fluences into expected hadronic neutrino yields. By combining these spectra with Trinity's effective area, we forecast observable event rates. Accounting for source duty cycles and environmental opacity, we aim to identify optimal observational targets to help guide future multi-messenger pointing strategies.

Speaker: Sameeksha Saini (Durham University)

200 TAMBO and TAMBITO: Progress Towards a Next-Generation Tau Neutrino Observatory

While IceCube has measured the flux of astrophysical neutrinos at energies up to several PeV, much remains to be learned about its origin and nature. Tackling these questions will require a new generation of novel observatory designs. TAMBO, the Tau Air Shower Mountain-Based Observatory, will comprise an array of 5,000 plastic scintillator detectors deployed along the face of a wide, steep canyon. This unique geometry will enable TAMBO to carry out low-background studies of tau neutrinos with energies above ~1PeV across a broad strip of the sky.

In this talk, I will discuss the physics sensitivities of TAMBO and its synergies with other next-generation neutrino observatories. I will also discuss recent progress on TAMBITO, the 100-module TAMBO demonstrator, including simulation development, detector optimization, and hardware prototyping.

Speaker: Carlos Argüelles (Harvard University)

Thursday, September 3

Plenary

201 Fundamental physics with IACTs and future prospects in the field

Imaging Atmospheric Cherenkov Telescopes (IACTs) have opened a new window on the very-high-energy gamma-ray sky, delivering unprecedented sensitivity at the lowest energies accessible from the ground. While these instruments are primarily designed for astrophysical studies, they also provide a powerful — yet still underutilized — laboratory for fundamental physics.
In this contribution, I will review the current status of such studies with IACTs, including investigations of new physics beyond the Standard Model (dark matter, axion-like particles, Lorentz invariance violation), searches for primordial black holes, as well as constraints on the extragalactic background light, investigations of intergalactic magnetic fields, and studies of cosmic rays using background data from gamma-ray observations. These results highlight the remarkable versatility of IACT data — but also expose an important structural limitation: they largely rely on observations optimized for other scientific goals.
Building on this overview, I will discuss the opportunities and limitations of this approach. While pursuing fundamental physics as an ancillary science case has proven productive, it introduces systematic biases in source selection, observation scheduling, and data analysis strategies that may be limiting our sensitivity in ways that are not always obvious. I will argue that a more deliberate consideration of observation strategies, source selection, and cross-instrument coordination could substantially enhance the reach of current and future facilities — without necessarily compromising their core astrophysical mission.
The field has made impressive progress precisely because IACT data is so rich and versatile. The question worth asking is whether the current approach — effective as it has been — is leaving sensitivity on the table for at least some of these topics, and whether a more deliberate, physics-driven design of observation programmes could open qualitatively new discovery potential for the coming generation of instruments.

Speaker: Tomislav Terzić (University of Rijeka, Faculty of Physics)

202 Multi-messenger models of AGN jets and coronae

Active galactic nuclei (AGN) are among the most powerful persistent sources of high-energy electromagnetic radiation in the Universe. The combination of large energy reservoirs, dense radiation fields and ionized plasma in AGN coronae, and relativistic plasma flows in AGN jets makes these systems prime candidates for the production of high-energy neutrinos. Indeed, most of the astrophysical neutrino source associations reported by the IceCube Neutrino Observatory involve AGN. In this talk, I will introduce the key structural components of AGN and outline the physical ingredients underlying multi-messenger models of their emission. I will then present modeling results for AGN jets and coronae, focusing on two representative sources: the GeV gamma-ray-bright blazar TXS 0506+056 and the nearby, TeV gamma-ray-dark Seyfert galaxy NGC 1068. These examples illustrate how neutrino production is shaped by the location of energy dissipation, the properties of the target photon fields, and constraints from X-ray and gamma-ray observations. I will discuss implications for the diffuse neutrino flux and conclude with key open questions in multi-messenger studies of AGN.

Speaker: Maria Petropoulou (National and Kapodistrian University of Athens)

10:30 AM break

Plenary

203 The WIMP Paradigm and Beyond: Status and Future Directions

The WIMP paradigm, in which dark matter particles are assumed to interact with the Standard Model and to have been thermalized in the early universe, remains one of the most compelling scenarios. It provides robust and testable predictions across a variety of interaction channels. Driven by significant experimental advances in both direct and indirect detection, increasingly precise theoretical calculations now enable the identification of dark matter signatures in observational data. In this talk, we review the current status and future prospects of the standard WIMP paradigm and discuss recent efforts to explore physics beyond it.

Speaker: Motoko Fujiwara (Kyushu University)

204 Cosmic Rays in the region of the Knee

Changes in the shape of the spectrum of cosmic rays, such as the "knee" in the 2-5 PeV range, have long been a clue to questions of their origin and propagation. For this energy regime, we will discuss experiments now exploring not only the cosmic ray energy spectrum, but also the particles' nuclear composition and potential multimessenger associations.

Speaker: Dr Katherine Rawlins (University of Alaska Anchorage)

12:00 PM Lunck

CR: CR6 : UHECR measurements

205 The Energy Spectrum of Ultra-High-Energy Cosmic Rays across Declinations from $-90^\circ$ to $+44.8^\circ$ Measured at the Pierre Auger Observatory

The energy spectrum of ultra-high-energy cosmic rays (UHECRs) above 2.5$\,$EeV is measured over the declination range $-90^\circ$ to $+44.8^\circ$ using 310,000 events from the Pierre Auger Observatory, corresponding to an exposure of $(104{,}900 \pm 3{,}100)\,\mathrm{km}^2\,\mathrm{sr}\,\mathrm{yr}$. The energy spectrum is studied as a function of declination to investigate possible variations across the sky. Within the statistical uncertainties, the spectra are found to be indistinguishable across declinations, after allowing or not for sky non-uniformities induced by the dipolar anisotropies in the arrival directions of ultra-high-energy cosmic rays. The high-statistics dataset enables a precise characterization of spectral features, including the ankle, the suppression at the highest energies, and a distinct ``instep'' feature at $\simeq 10~\mathrm{EeV}$. The instep is established with a significance above $5\sigma$, strengthening previous evidence. The absence of any declination dependence disfavors an interpretation in which the instep arises from a small number of distinctive sources. This presentation focuses on the analysis strategy adopted in this measurement and on some of the implications of these results.

Speaker: Fabio Convenga (GSSI & LNGS)

206 Recent results on ultra-high-energy cosmic rays from the Telescope Array experiment

The Telescope Array (TA) is the largest cosmic-ray observatory in the Northern Hemisphere. With the main goal of determining the origin of cosmic rays, it is designed to measure the properties of cosmic rays over a wide energy range. Together with its low-energy extension, TALE, TA observes cosmic-ray-induced extensive air showers from 2×10^15 to 2×10^20 eV in hybrid mode, employing a surface array of scintillator detectors (SD) and telescopes to measure the fluorescence and Cherenkov light. To increase statistics at the highest energies, the TAx4 expansion is currently under construction, which will quadruple the detector’s effective area. We present the current status of the TA, TAx4 and TALE experiments, along with the most recent physics results. Notable highlights include mass composition measurements in hybrid mode between 10^16.5 and 10^18.5 eV from TA and TALE, and ultra-high-energy photon flux limits obtained using novel machine learning techniques, correlations of ultra-high-energy cosmic rays with BL Lac type objects. The interdisciplinary results on Terrestrial Gamma-Ray Flashes observed at the TA SD will also be shown.

Speaker: Grigory Rubtsov (INR RAS)

207 Latest Measurement of the Ultra High Energy Cosmic Ray Spectrum with the Telescope Array Surface Detector

Ultra-high-energy cosmic rays (UHECRs) are the most energetic charged particles observed in nature, but their sources and propagation processes are still not fully understood. The Telescope Array (TA) experiment, the largest UHECR observatory in the Northern Hemisphere, has achieved high-precision measurements of the cosmic ray energy spectrum through stable long-term operation and efficient data collection. These measurements reveal three prominent spectral features—the ankle, the shoulder, and the cutoff—which provide important insight into the origin and propagation of UHECRs. In this contribution, we present the latest energy spectrum measured with the TA surface detector array and discuss the observed differences between the UHECR energy spectra in the northern and southern skies.

Speaker: Jihyun Kim (Osaka Metropolitan University)

208 Measurement of the depth of the maximum of air-shower profiles above 10^17.7 eV at the Pierre Auger Observatory

The Pierre Auger Observatory has been measuring extensive air showers produced by ultra-high-energy cosmic rays (UHECRs) for over two decades. While significant progress in this field has been made, the sources, acceleration mechanisms, and hadronic interactions at these energies still remain poorly understood. A key property for constraining these open questions is the mass composition of the primary particles. By detecting the longitudinal profiles of the air showers, the mass composition can be inferred from the distributions of the depth of the shower maximum, Xmax, the atmospheric depth at which the shower reaches its maximum energy deposition. Using 18 years of high-quality profiles measured with the Fluorescence Detector, the Pierre Auger Collaboration has performed a detailed study of the mass composition above 10^17.7 eV. In this talk, we summarize the main results of this analysis and discuss their implications for the origin and nature of UHECRs.

Speaker: Nikolas Denner (FZU - Institute of Physics of the Czech Academy of Sciences)

209 Hadronic interaction studies at the Pierre Auger Observatory

Ultra-high-energy cosmic rays (E > $10^{18}$ eV) are the most energetic particles in the Universe and, as such, provide a unique opportunity to probe hadronic interactions at energies beyond those reached at the LHC. Due to their extremely low flux, these cosmic rays can only be studied indirectly through extensive air showers (EAS), cascades of secondary particles produced when a primary cosmic ray interacts with a nucleus in the atmosphere. The primary mass must therefore be inferred from EAS observables recorded by large ground-based detectors. The main mass-sensitive observables are the atmospheric depth at which the electromagnetic component reaches its maximum, $X_{\max}$, and the number of muons, $N_\mu$. More challenging to measure, the atmospheric depth at which muon production reaches its maximum, $X^{\mu}_{\max}$, also provides sensitivity to the primary mass. The mass composition is inferred by comparing measurements of these observables with air-shower simulations based on hadronic interaction models, which extrapolate collider data to ultra-high energies. Several experiments have reported a tension between the mass composition inferred from $X_{\max}$ and that derived from $N_\mu$ and $X^{\mu}_{\max}$. This discrepancy is commonly interpreted as a deficit of muons in simulations, indicating that the hadronic component of EAS -where muons are produced- is not accurately described by current hadronic interaction models. The Pierre Auger Observatory is the largest cosmic-ray observatory in the world. Its hybrid design enables the measurement of $X_{\max}$ with the Fluorescence Detector, while the Surface Detector provides sensitivity to $N_\mu$ and $X^{\mu}_{\max}$. In this contribution, we present a summary of hadronic interaction studies performed at the Pierre Auger Observatory over more than 20 years of operation.

Speaker: Joaquin de Jesus (IGFAE - University of Santiago de Compostela)

210 MCEq: Latest Updates and Seasonal Variations

Accurately modeling the atmospheric lepton fluxes plays a crucial role for astrophysical neutrino search, neutrino oscillations studies, probing hadronic interaction models, beyond-standard-model searches, and tools such as muon tomography. In this talk, I present the latest update of the flux modeling code MCEq (Matrix Cascade Equations), featuring an updated particle yield and cross-section database supporting the most recent generation of hadronic interaction models SIBYLL-2.3e, EPOS-LHC-R, and QGSJet-III. Using MCEq and MUTE (MUon inTensity codE) I demonstrate the frameworks application to seasonal variation studies and compare its aspects with the common $\alpha_T$ approach. Furthermore, future applications and advanced flux modeling for MCEq are outlined.

Speaker: Stefan Fröse (Institute of Physics, Academia Sinica)

DM: DM7 : Dark Matter Theory and BSM Connections

211 Sub-GeV Scalar Dark Matter in a Higgs-Mixed Dark Sector: From Neutrino Masses to Astrophysical Signals

We investigate sub-GeV scalar dark matter embedded in a rich dark sector linking cosmology, neutrino physics, and astrophysical observables. The framework features a complex scalar dark matter candidate interacting via a Higgs-mixed mediator associated with the spontaneous breaking of a dark $U'(1)$ symmetry.

We first perform a numerical exploration of the scalar and dark matter sector and identify regions of parameter space where thermal production can reproduce the observed relic abundance while remaining consistent with existing constraints. We then extend the model by introducing a sterile neutrino and a pair of dark neutrinos charged under the broken symmetry. A large-scale numerical scan reveals viable regions where the mediator can decay before Big Bang Nucleosynthesis while simultaneously generating sub-eV active neutrino masses.

Finally, we discuss the phenomenological implications of this framework, including potential connections to the Galactic 511 keV line, and to gravitational-wave signals from the dark-sector phase transition.

Speaker: Elina Merkel (University of Bologna, INFN Bologna)

212 Boosted dark matter from semi-annihilation in a neutrino mass model

Dark matter particles can be accelerated by annihilation processes such as semi-annihilations and $n \to m$ ($n > m$) processes when the dark sector is non-minimally extended. Such boosted dark matter can provide a distinctive signature of a non-minimal dark sector, and its experimental detectability has been explored in a model-independent manner in previous work. In this work, we construct an explicit model of boosted dark matter originating from semi-annihilations. A Dirac fermion is identified as the dark matter candidate, which semi-annihilates into a pair of an anti-dark matter particle and a neutrino. The small neutrino masses are also radiatively generated at the two-loop level. Taking into account the relevant experimental and theoretical constraints, we find that the mass of the mediator needs to be $\mathcal{O}(1),\mathrm{MeV}$ for elastic scattering with nucleons, so that the cross section is enhanced to $\mathcal{O}(10^{-36}),\mathrm{cm}^2$, allowing detection in future experiments such as DUNE and DARWIN.

Speaker: Takashi Toma (Kanazawa University)

213 Hidden Sector Dark Matter and the Galactic Center Gamma-Ray Excess

In hidden sector models, the dark matter does not directly couple to the particle content of the Standard Model, strongly suppressing rates at direct detection experiments, while still allowing for detectable signals from dark matter annihilation. I will describe a variety of portal interactions that can allow the hidden sector annihilation products to decay into Standard Model particles and apply these results to the observed Galactic Center gamma-ray excess. In contrast with what has sometimes been claimed in the literature, annihilation cross sections of order σv ∼ 10^-26 cm^3/s are a generic feature of hidden-sector dark matter models, even if the dark matter was decoupled from the Standard Model bath at the time of its thermal freeze-out. As a consequence, the coupling between the Standard Model and the hidden sector can be extremely small, potentially placing direct detection and collider signals far below foreseeable sensitivities.

Speaker: Dan Hooper (University of Wisconsin-Madison)

214 Illuminating the Dark Sector: Confirming the 20 GeV Halo and Probing Its Mediator

Totani recently reported a spherically symmetric, halo-like component of the Galactic diffuse emission peaking near $20\,$GeV in fifteen years of $\textit{Fermi}$--LAT data, extracted at high latitude, where the diffuse backgrounds are cleanest, and compatible at the template level with dark matter annihilation in a smooth NFW halo.

We test that result with an independent pipeline. Reproducing the cellwise analysis and extending it to a global pixel-level likelihood on the native $0.125^{\circ}$ maps, including energy-dependent PSF forward folding, bright-source masking, and an exact per-pixel Poisson treatment across 17 years of Pass~8 data, we recover the same $20\,$GeV halo, about $20\%$ higher in normalisation and unchanged in shape. It is centrally concentrated rather than isotropic, and spectrally and morphologically distinct both from the Galactic Centre excess and from any millisecond-pulsar population. A full systematic budget shows the measurement is limited by the diffuse foreground model, not by statistics.

Read as dark matter, the excess implies $m_{\chi} \approx. 0.55$--$0.72\,$TeV with a dwarf-spheroidal tension $\mathcal{R} \approx. 5.1$, widened to $1.6$--$9.3$ once foreground and
$J$-factor uncertainties are included. Mass freedom does not close it; $p$- and $d$-wave annihilation are excluded by the relic abundance, and a decay interpretation by the isotropic gamma-ray background. Only low-velocity-enhanced annihilation reconciles the present-day halo rate, the dwarf limits and freeze-out simultaneously. This supplies the required $\approx. 45\times$ boost through the relic abundance rather than by weakening the dwarf constraint, and demands a sub-GeV mediator.

We close on the crossed channel of that annihilation: elastic photon--dark-matter scattering along the same line of sight, linear rather than quadratic in the dark matter density. The real-photon operator basis collapses to dipole and Rayleigh structures, anapole and charge
radius vanish identically on shell, which sorts the halo's candidate mediators before any data are used. We present the first operator-resolved photon--dark-matter scattering limits from astrophysical gamma-ray data.

Speaker: Trinity Stenhouse (UCL)

215 Learning the Propagation of Cosmic Rays from Dark Matter with Neural Networks

Accurate modeling of cosmic-ray propagation in the Galaxy is a central ingredient in indirect searches for dark matter. However, numerical propagation codes are computationally expensive, limiting their applicability in large parameter scans and inference studies. In this talk, I will present a novel neural network framework that learns the mapping between arbitrary dark matter antiproton or antideuteron injection spectra and the corresponding propagated fluxes at Earth. Our approach is fully agnostic to the underlying injection spectrum and instead directly operates on the spectral shape. The network takes as input both the injection spectrum and the relevant propagation parameters, enabling fast and flexible predictions across a wide parameter space while still accurately reproducing the results of state-of-the-art propagation codes.

Speaker: Lena Rathmann (KIT)

GR: GR7 : AGNs

216 Potential of Miniature Radio Galaxies at HE/VHE domain

In the 1960s, Third Cambridge Catalogue (3C) provided the first demonstration of radio galaxies (RGs). Radio galaxies with active nuclei were soon classified as Fanaroff-Riley (FR) type I or II. Most of our knowledge on RGs have come through these powerful sources. However, advances in observational techniques have revealed that the majority of the jetted AGN population in the local universe is dominated by “miniature” versions of RGs. These miniature RGs (MiRG) generally show no extension in radio images with arcsecond resolution and too low a radio power to be nascent versions of the 3C sources. Still, they occupy the same host galaxies as the more powerful 3C/FRI sources, show similar distribution of BH masses and even display the same correlation between radio and optical luminosities, extending the one observed for 3C/FRI to lower radio powers. In light of these similarities, reinforcing the hypothesis of a single accretion/ejection mechanism across radio galaxies of all powers, these compact sources were labelled as Fanaroff Riley 0 (FR0). FR0s were identified at even lower radio powers in sources categorised as Core Galaxies. The large abundance of these sources and their similarities to FR-I RGs, together with the fact that all RGs detected at VHE to date are low-power FRI RGs, highlights their importance as a potential population of HE/VHE emissions. In addition, the enhanced sensitivities of upcoming facilities, such as the prototype large-size telescopes of the Cherenkov Telescope Array will significantly improve our observational capabilities and allow for detection of more such sources. In this contribution, I will present a large sample of MiRG and discuss their high-energy properties, placing them in the broader context of traditional FR RGs. I will also discuss the possibility of identifying new such sources at HE/VHE domain, building upon the few sources that have been detected.

Speaker: Udai Sharma (IFAE)

217 Search for correlations between Fermi-LAT very high energy photons and active galactic nuclei

In this work study of possible correlations between very high-energy Fermi LAT photons and active galactic nuclei is presented. Two main issues related to this field of studies are are background modeling and the non‑uniform sky distribution of sources. Approach used in this analysis is data‑driven: background is estimated empirically and associations between photons and candidate sources are tested with the use of correlation methods that look for deviations from isotropy. This framework provides controlled significance estimates and can be applied to other source classes. Preliminary results and sensitivity are discussed.

Speaker: Mariia Kudenko (Institute for Nuclear Research Russian Academy of Science)

218 Probing CO-dark Gas and Blazar Jet Power with ALMA Calibrators: Toward the Origin of High-Energy Neutrinos

Identifying the origin of TeV-PeV neutrinos requires understanding both how much target material is available for hadronic interactions and where high-energy emission originates in blazar jets. While excess neutrino emission toward the Galactic Center suggests that dense gas environments play an important role, the association of a high-energy neutrino with the blazar TXS 0506+056 indicates that relativistic jets can also accelerate cosmic rays. In both cases, the key quantities governing neutrino production, namely target density and particle acceleration power, remain poorly constrained.

We present a new observational approach based on the ALMA Calibrator Source Catalogue, a large and homogeneous dataset of bright blazars and background continuum sources, which allows us to probe both ingredients in a unified way. First, absorption-line measurements toward ALMA calibrators reveal diffuse molecular gas, including CO-dark components missed by conventional emission-line surveys, and thus provide direct constraints on the target density for cosmic-ray interactions. Second, using a statistically significant sample of ALMA-Fermi matched blazars, we find a strong correlation between millimeter and gamma-ray luminosities, indicating that millimeter emission traces the average jet power and particle acceleration efficiency. Taken together, these results demonstrate that ALMA calibrator observations provide a unique framework for linking target environments and jet energetics in the study of gamma rays and high-energy neutrinos.

Speaker: Kanako narita (The University of Tokyo)

219 The VERITAS TeV AGN Catalog

VERITAS is one of the world’s most sensitive very-high-energy (VHE; E > 100 GeV) gamma-ray observatories. Approximately half of its observations are targeted on active galactic nuclei (AGN). We will describe our recent efforts to reprocess the historical archive of these AGN observations and produce a standardized, first VERITAS TeV AGN Catalog. We will present the current status of catalog, including results, and will describe recent new detections and discoveries of AGNs at VHE using VERITAS.

Speaker: Juan Escudero Pedrosa (Harvard-Smithsonian Center for Astrophysics)

220 Investigation of long-term data from the MAGIC Telescopes using database-driven automation tools

The acceleration mechanisms powering the emission of high-energy gamma-rays within the jets of active galactic nuclei are continuously the target of investigations by the astroparticle physics community. While not yet fully understood, the community has advanced its knowledge of the classification of the acceleration processes, among other things, through the analysis of data from Imaging Air Cherenkov Telescopes (IACT). Notably, the analysis of data from highly luminous BL Lac sources, which form a subclass of blazars, allows for insights into the spectra and acceleration process classification in the high-energy regime between 100 Gev and 30 TeV.

To dive deeper into the astrophysical understanding of these objects, it becomes necessary to analyze larger amounts of data, corresponding to timescales much longer than a typical analysis. However, the data of the MAGIC Telescopes that is used within this analysis is continuously influenced by the variability of the night-sky background, weather, and zenith of the source, since IACTs utilize Earth's atmosphere as their detector volume. This makes the analysis more time-intensive with respect to the parameter space of interest than that of atmosphere-independent satellite observatories, like FERMI.

In order to tackle this challenge in data processing, the database-driven automation software autoMAGIC is being developed. This tool offers the possibility to reliably analyze larger timescales of data featuring broad parameter spaces with respect to observational data-taking parameters, in a reproducible manner. Utilizing autoMAGIC, this talk will present the analysis of long-term data of chosen BL Lac objects from the MAGIC Telescopes, give insights into the spectral parameters of the source throughout the extent of the analyzed timeframe of MAGIC data and demonstrate its promise for the data legacy of the MAGIC Collaboration.

Speaker: Cyrus Walther (TU Dortmund University / LAMARR Institute)

GW: GW2 : Multi-Messenger, PBH and New Physics

221 Gravitational-Wave signals in Pulsar Timing Array from Confined Flux Tubes as Cosmic Strings

We consider a pure Yang-Mills theory with $\mathrm{Spin}(4N) (N\geq2)$ gauge group.
In this framework, color flux tubes are stable against breaking due to the absence of dynamical matter in the fundamental representation.
If confinement occurs after inflation, the phase transition produces color flux tubes with typical separations set by the Hubble scale, allowing them to extend to cosmological length scales.
These flux tubes then behave as cosmic strings with small reconnection probabilities.
We study the dynamics of these cosmic string networks by the extended Velocity-dependent One Scale (VOS) model.
In particular, we show that delayed scaling modifies the gravitational-wave spectrum, making it easier to account for  the observed signal by Pulsar Timing Array such as NANOGrav without conflicting with limits from LIGO-Virgo observations.

Speaker: Kazuto Nakamura (Department of Physics, Tohoku University, Japan)

222 LISA can detect dark matter subhalos through gravitational-wave lensing

Strongly lensed gravitational waves offer a new way to study dark matter structure on subgalactic scales. In the wave-optics regime, gravitational waves propagating through a population of dark matter subhalos acquire frequency-dependent amplitude and phase distortions that encode the small-scale matter distribution along the line of sight.

We compute the full diffraction integral for gravitational waves propagating through statistically generated cold dark matter subhalo populations embedded in realistic galaxy-scale lenses, and evaluate the resulting signals in the LISA band. We find that strongly magnified images generically exhibit percent-level wave-optics modulations induced primarily by subhalos with masses in the range $10^4–10^7\,M_\odot$.

These signatures arise naturally within the standard cold dark matter paradigm and should be detectable in high–signal-to-noise strongly lensed LISA events. Strongly lensed gravitational waves therefore provide a direct and complementary probe of dark matter substructure at mass scales that are difficult to access with conventional electromagnetic lensing observations.

Speaker: Shin'ichiro Ando (GRAPPA, University of Amsterdam)

223 Can Torques Save Primordial Black Hole Spikes?

Density spikes are steep enhancements in the dark matter (DM) distribution that arise from gravitational infall onto a central compact object. In the standard scenario where DM consists of particles, such spikes may form around a sub-dominant population of massive primordial black holes (PBHs), potentially leading to large enhancements of the DM density in their vicinity.

The situation can be qualitatively different if, instead, the bulk of the DM is also composed of PBHs, which are viable alternative candidates to particle DM and can constitute the entirety of it if, for example, they have masses around $M \sim 10^{17}-10^{22}\,\mathrm{g}$. In this scenario, lighter PBHs may avoid capture only if they develop enough angular momentum as a consequence of the torques exerted by both small-scale and large-scale fluctuations.

We investigate the mechanisms and initial conditions—such as the mass and initial separation from a central heavy PBH ($M \sim M_\odot$)—that enable lighter PBHs ($M \sim 10^{18}$–$10^{28}\mathrm{g}$) within such spikes to develop long-lived density enhancements. More specifically, we characterize the torque distribution and its evolution, and follow the resulting angular momentum dynamics using a combination of analytical approaches and numerical simulations.

Speaker: Agnese Tolino (IFIC (CSIC-UV))

224 Searching for Very-High-Energy Gamma Rays from Binary Black Hole Mergers with VERITAS

Since the joint detection of gravitational waves from GW 170817 and electromagnetic radiation from a short gamma-ray burst, GRB 170817A, the multimessenger community has worked extensively to investigate these events. This detection showed that binary neutron star mergers are progenitors of short GRBs and demonstrated the advantages of multimessenger observations. Although GRB 170817A was observed across the electromagnetic spectrum, it was not detected in the very-high-energy (VHE; >100 GeV) energy range. This raises the question of whether a VHE counterpart to these mergers exists, as well as the possibility of electromagnetic emission from other GW events such as binary black hole (BBH) mergers. The Very Energetic Radiation Imaging Telescope Array System (VERITAS), a ground-based telescope in southern Arizona, is sensitive to VHE gamma rays and is capable of rapid follow-up observations of GW alerts. Here, we perform a population-level search for VHE gamma rays from BBH mergers reported in the LIGO-Virgo-KAGRA (LVK) Gravitational-Wave Transient Catalog and studied with VERITAS. We use 3D localization maps from LVK to account for the 90% credible regions, distance posteriors, and VERITAS sky coverage for each event. With this information, we calculate the gravitational-wave energy emitted in each event and place upper limits on the isotropic-equivalent gamma-ray energy to constrain the fraction of merger energy that must be emitted in VHE gamma rays for detection. We produce a probability detection curve to determine the fraction of merger energy that would need to be emitted in VHE gamma rays for VERITAS to have a 95% or greater probability of detecting at least one event in our list of GW events. Constraining the amount of VHE emission can provide insight into the environment of BBH mergers and the possible emission mechanisms that produce VHE particles in these extreme events. This framework provides a foundation for future GW-triggered VHE searches.

Speaker: Madalyn Johnson (University of California Santa Cruz)

225 Sub-threshold searches for coincidences between gravitational waves and neutrino detected with neutrino telescopes in the depths of the Mediterranean Sea

Astrophysical neutrinos are expected to be produced during transient phenomena that also produce gravitational waves, such as compact binary coalescences, in particular those involving neutron stars, or core-collapse supernovae. Gravitational waves are routinely detected by the LIGO-Virgo-KAGRA interferometers, while the ANTARES and KM3NeT deep-sea neutrino telescopes are sensitive to neutrino interactions in a wide range of energies, from MeV to PeV. The contribution overviews sub-threshold searches for neutrino triggers observed in temporal and spatial correlation with gravitational wave triggers. This analysis employs a Bayesian metric to rank associations between high-energy neutrino and gravitational wave triggers. Backgrounds are modelled from data by shifting the timings of the neutrino and gravitational wave triggers, and are used to assign a false-alarm rate to the neutrino-gravitational wave associations. Here, these associations are investigated using public LIGO-Virgo-KAGRA data from the O3 run together with data collected by the ANTARES and KM3NeT-ORCA detectors during the corresponding period.

Speaker: Pierre-Alexandre DUVERNE (APC, Université Paris Cité)

MM: MM7 : Modeling of Particle Emissions

226 Clustering the Interstellar Medium for Galactic Gamma-Ray Modelling

To reveal the nature of high-energy, gamma-ray sources and identify the associated accelerator and production mechanisms, we need detailed models capable of reproducing observed energy spectra and morphologies. To produce these gamma-ray models in a hadronic scenario, we need cosmic-ray and ISM distributions in 3D, as the gamma-ray morphology is sensitive to the relative distances between the accelerator and ISM gas clouds. However, these distances are typically not known with the precision we require. Our novel approach is to iterate over the distances of individual ISM clouds. To facilitate this, the 3D pixels belonging to a specific cloud structure are identified using clustering.

In this contribution, we will present results from our 3D molecular hydrogen distributions of ISM cloud structures, derived over the entire Mopra Southern Galactic Plane CO Survey. We will introduce our novel cloud identification method used to create these distributions. This involves Gaussian decompositions and clustering, as well as combining measurements from different gas tracers ($^{12}$CO and $^{13}$CO). We will also demonstrate how iterating over the physical distances to the cloud structures in our ISM maps, can significantly improve gamma-ray modelling.

Speaker: Imogen Barnsley (Adelaide University)

227 Variety of disk wind-driven explosions in massive rotating stars

Massive stars are intriguing objects and key players in the cosmic cycle, yet they not totally understood, especially their fate. They, in fact, distinguish themselves from lower mass stars by the events that can take place at their death. While the majority of stars will fade away as white dwarfs, massive stars with an initial mass $\geq 8\,M_\odot$ at the end of their evolution form a degenerate iron core which collapses into a proto-neutron star (PNS). This is the starting point for a complex sequence of events with many possible outcomes. Less to moderately massive stars (with $8\lesssim M\lesssim 16\,M_\odot$) are expected to undergo an explosion during the PNS phase as core-collapse supernova (CCSN), whereas in more massive star (M $\gtrsim$16M$_\odot$) it is likely that the initial shock energy cannot disrupt the entire star, leading to a final collapse forming a black hole (BH). This event is known as ``failed supernovae''. The failed collapse could represent the end of the phenomena, unless another ingredient is added: the rotation. In case the progenitor is a massive rotating star, an accretion disk can be formed around the BH, in turn generating a disk wind. This wind has been thought as being of a sufficient energy to expel the remaining part of the star, being the source of a super energetic explosion with an energy $E_\mathrm{expl}>10^{52}$ erg and has been found to be rich in $^{56}$Ni.
In this collapsar scenario the properties of the ejecta and the $^{56}$Ni production are strongly related to the wind injection from the accretion disk and these properties had not yet been studied in a systematic manner until our latest work. Moreover these collapsar-driven explosions are associated with broad-lined Type Ic supernovae (Ic-BL SNe) and, in some cases, long gamma-ray bursts (GRBs).

Understanding the nature of these explosions requires detailed numerical modeling, capturing the formation and evolution of the central engine, the propagation of relativistic outflows, and the resulting observational signatures. In this talk, I will present our last study of the ejecta generated by the collapse of rotating massive stars, with a focus on the late-phase mass ejection after BH formation. I will do that by systematically exploring the effects of progenitor mass, rotation, and the properties of the injected wind on the dynamics of the ejecta and the production of $^{56}$Ni.This study is based on several two-dimensional hydrodynamics simulations of axisymmetric models of the ejecta generated by the collapse of rotating massive stars performed using the code \texttt{Athena++}. Based on the collapsar scenario, we assume an explosion powered through a BH-accretion disk system and investigate the impact of the disk mass and energy injected from the system on the final ejecta.

Our results focus on the distribution of the explosion energy and the injected energy of different progenitor models and on the $^{56}$Ni production computed through a particle tracing. We find a tight correlation between $E_\mathrm{expl}$ and $M_\mathrm{ej}$ and a bimodality of the explosions energy will explain in my talk. I will support our results with comparison to the observational data.

By mapping the parameter space of collapsar-driven explosions, our study sheds light on the conditions required to produce highly energetic supernovae and GRBs. We find that the diversity in explosion properties observed in broad-lined Ic SNe can be naturally explained by variations in the accretion disk characteristics and progenitor structure. Our models also suggest a possible link between long GRBs and failed SN. By extending our models to different initial conditions and varying key parameters, we aim to establish a more comprehensive understanding of the pathways leading to extreme stellar explosions. Our work provides a theoretical framework to interpret current and future observations, offering predictions that can be tested with upcoming surveys and multi-messenger facilities.

Speaker: Ludovica Crosato Menegazzi (Deutsches Elektronen-Synchrotron (DESY) - Zeuthen)

228 An updated proto-neutron star neutrino emission model

We present an improved parametric model for neutrino emission from core-collapse supernovae that directly connects neutrino luminosity and average energy to stellar properties during the emission. Our model incorporates two critical physical processes: convection within the proto-neutron star (PNS) and the evolving dynamics of neutrinosphere radii during the early emission phase. Crucially, the evolution of the PNS radius is tied to its gravitational-wave signature, providing a stronger physical framework for joint neutrino and gravitational-wave searches of the next Galactic supernova.

Speaker: Matteo Ballelli (Gran sasso science Institute (GSSI))

229 On the optical-neutrino synchronized observation of interaction-powered supernovae

In recent years, there are some reported supernovae whose observational time and direction are close to high-energy neutrino events detected by IceCube. High-energy neutrinos from supernovae are theoretically supported by a shock and circumstellar medium (CSM) interaction scenario. We focused on one of such synchronized observations, SN 2023uqf —a Type Ibn supernova—, that was reported to be temporally and spatially consistent with IC-231004A —the 442 TeV neutrino alerted by IceCube—. One-dimensional radiation-hydrodynamics calculations in a dense helium-rich CSM are performed with STELLA to reproduce the optical curve by ZTF. We then calculate high-energy neutrino production based on the shock evolution and CSM conditions inferred from the optical observation. In addition, we discuss the detection chance at IceCube as well as the diffuse neutrino flux contributed by interaction-powered supernovae.

Speaker: Yosuke Ashida (Tohoku University)

3:30 PM break

BSM: BSM2 : Neutrino Properties and Lorentz Symmetry

230 Leptogenesis from a Type-I Seesaw Model Predicting Modified TM2 Mixing

One of the greatest outstanding mysteries in physics is the observed baryon asymmetry of the Universe. Experimental constraints have made it clear that neither CP asymmetry in the quark sector, nor CP asymmetry in the lepton sector, are sufficient to explain the size of the observed baryon asymmetry. One viable explanation is the leptogenesis mechanism of Fukugita and Yanagida wherein lepton asymmetry originates in the early universe through out-of-equillibrium decays of heavy right handed neutrinos. This is then in turn converted into baryon asymmetry via the sphaleron process. We present an leptonic mass Lagrangian containing 3 heavy right handed neutrinos which leads to the required degenerate Majorana mass matrix neccescary for leptogenesis. It is also constructed so that it is diagonalizeable by a PMNS matrix whose value’s magnitudes are within 1-sigma of current experimental values. This is done by deviating from a Lagrangian whose mass matrix diagonalable by TM2. We then investigate some of the phenomenological consequences of this model.

Speaker: Michael Fodroci (Tokai University (東海大学))

231 Signatures of Quasi-Dirac Neutrinos In Neutrino Telescopes

Whether neutrinos are Dirac or Majorana remains one of the deepest open questions in particle physics. An especially compelling possibility is that they are quasi‑Dirac: each active neutrino paired with a nearly degenerate sterile partner, split by a tiny Majorana mass plausibly generated by Planck‑scale or string‑theoretic lepton‑number violation. The signature is an ultra‑long‑baseline active‑to‑sterile oscillation, far beyond the reach of terrestrial experiments but naturally probed by the cosmological distances traversed by astrophysical neutrinos. We summarize three complementary studies that exploit neutrino telescopes to test this scenario: one using IceCube's observation of the point source NGC 1068, one using the diffuse all‑sky astrophysical flux, and one forecasting the reach of IceCube and KM3NeT measurements of Galactic neutrinos. Together, they show that neutrino telescopes — across point‑source, diffuse, and Galactic channels — can probe the quasi‑Dirac hypothesis over a vast range of mass splittings inaccessible to any other experiment, opening a direct window on Planck‑scale physics through the oscillations of cosmic neutrinos.

Speaker: Carlos Argüelles (Harvard University)

232 OνDES - Probing Solar Neutrino BSM Physics with Cryogenic Scintillating Calorimeters

Cryogenic scintillating calorimeters (CSCs) with transition-edge sensor (TES) readout have demonstrated excellent sensitivity to dark matter–nucleus and neutrino–nucleus scattering. The OνDES project extends this technology to lower energy thresholds, enabling searches for dark matter–electron and neutrino–electron scattering.

In this talk, I will introduce the OνDES project and the theoretical framework developed for neutrino–electron scattering searches with CSCs. I will present preliminary sensitivity projections for probing beyond-the-Standard-Model (BSM) neutrino interactions and discuss the status of the first experimental prototype currently under development within the COSINUS collaboration.

Speaker: Elisa Gaido (Max Planck Institute for Physics)

233 Search for Lorentz-Invariance Violation with gamma-ray bursts and neutrinos from ANTARES

As a consequence of deviations from special relativity, Lorentz-Invariance Violation may affect the propagation of astrophysical neutrinos. In particular, it may introduce an additional shift with respect to the intrinsic time delay between neutrino detection and the signature of another messenger, and the possible faster-than-light component would be subject to decay, affecting the observable flux. Since the neutrino emission of gamma-ray bursts is expected in a relatively short time frame, they are ideal sources for investigating such effects. A positive detection would confirm the emission of neutrinos from these sources and open a yet unexplored territory beyond the standard paradigm.

Data collected by the ANTARES undersea neutrino telescope between 2007 and 2022 were analyzed to identify potential associations with cataloged gamma-ray bursts, taking into account the compatibility between neutrino arrival times and their possible decay. The presentation will detail the unbinned likelihood approach used for this analysis, its results, and the related prospects.

Speaker: Mathieu Lamoureux (APC)

234 Very-high-energy emission of the Crab Pulsar and tests for Lorentz Invariance Violation

Several Quantum Gravity models allow for a spontaneous violation of Lorentz Invariance close to the Planck scale, leading to non-trivial energy-dependent dispersion relations for the photon in vacuum. As a result, gamma-rays emitted simultaneously at different energies that travel very long distances can potentially accumulate different measurable delays in their time of flight towards the Earth. In the case of pulsars, such an effect would be revealed as an energy-dependent pulse shift in their phaseogram. The Major Atmospheric Gamma Imaging Cherenkov (MAGIC) Telescopes have been observing the Crab Pulsar since 2004. In this study, we present new constraints on the effective Lorentz Invariance violating energy scale based on a data set with over 300 hours of stereo data collected from 2009 until 2020. Our approach involves a profile likelihood analysis of pulsar events reconstructed with energies ranging from <100 GeV to ~1 TeV. In addition, other characteristics of the Crab Pulsar's emission profile are explored, including an investigation of the intrinsic pulse shape, which could offer new insights into pulsar behaviour at VHE. This study implements an energy-dependent optimisation of the MAGIC standard analysis to improve sensitivity at very high energies, offering a unique opportunity to investigate the long-standing question of a potential TeV extension of the pulsar emission.

Speaker: Anna Campoy Ordaz (Universitat Autònoma de Barcelona and CERES-IEEC)

235 Bounds on Lorentz invariance violation from muon fluctuations at the Pierre Auger Observatory

Lorentz invariance may be modified in quantum gravity scenarios, potentially leading to observable effects even far below the Planck scale. Ultra-high-energy cosmic rays provide a unique laboratory to probe such deviations. In this contribution, we exploit, for the first time, fluctuations in the muon content of extensive air showers measured at the Pierre Auger Observatory to constrain Lorentz invariance violation in the hadronic sector. The resulting bounds are the most stringent to date and are obtained without assumptions on the mass composition of ultra-high-energy cosmic rays. These results establish muon fluctuations as a powerful and complementary observable, opening a new window to probe Lorentz invariance in previously unexplored regions of parameter space.

Speaker: Caterina Trimarelli (GSSI-LNGS-INFN)

CR: CR7 : Galactic Cosmic-Rays II

236 All-Particle Cosmic-Ray Spectrum in the 10-300 TeV Range with the ALPAQUITA Air-Shower Array

We report a measurement of the all-particle cosmic-ray energy spectrum with the ALPAQUITA array, the prototype of the ALPACA experiment, located at an altitude of 4,740 m on Mount Chacaltaya in Bolivia. The array consists of 97 scintillation detectors deployed on a 15 m grid. Using approximately 240 days of data, we measure the cosmic-ray flux in the energy range from 10 TeV to 300 TeV. This energy range overlaps with space-based measurements and indirect measurements by ground-based air-shower arrays. In this contribution, we present the event reconstruction, the energy estimation, and the detector performance evaluation, and show the resulting all-particle spectrum. We also compare our results with previous direct and indirect measurements.

Speaker: Keitaro Fujita (Osaka Electro-Communication University)

237 Energy Reconstruction and Background Rejection for Cosmic-Ray Electron Observation above 10 TeV with the Tibet AS$\gamma$ Array

The energy spectrum and arrival direction anisotropy of high-energy
cosmic-ray electrons above 1 TeV serve as crucial probes for identifying
nearby acceleration sources. The Tibet AS$\gamma$ experiment, an air
shower array located at an altitude of 4,300 m, aims to observe cosmic-
ray electrons in the energy region above 10 TeV.

In this study, we developed an energy determination method and a
rejection technique for hadronic cosmic rays using Monte Carlo
simulations. By optimizing energy estimation tables specifically for
cosmic-ray electrons, we achieved an energy resolution of 40% at
approximately 10 TeV and 15% at 100 TeV. The energy bias was confirmed
to be within 3% across the entire range from 10 to 100 TeV. Furthermore,
simulations demonstrated that at around 10 TeV, selecting only events
whose shower core hits the area covered by the underground muon
detectors improves the signal-to-noise ratio for background rejection
through muon cuts, even though it results in a reduction of the total
statistics.

In this presentation, we report on the details of these simulation
results and discuss the feasibility of observing cosmic-ray electrons
with the Tibet AS$\gamma$ experiment.

Speaker: Naru Tamaki (University of Tokyo)

238 Highlights from the AMS Experiment (1): Precision measurements of cosmic nuclei from hydrogen to nickel

We report the properties of cosmic ray nuclei from protons to nickel (Z=1--20, 26, and 28) in the rigidity range from 2 GV to 3 TV
collected by the Alpha Magnetic Spectrometer (AMS) on the International Space Station during 15 years of operation. AMS is the
only magnetic spectrometer in space. Unexpectedly, the twenty-one element measured by AMS, from He to Ca and Fe, Ni can be
categorized into four classes, two primary and two secondary, based on their rigidity dependence. AMS found that the primary cosmic
rays He-C-O-Fe-Ni, and Ne-Mg-Si-S belong to two different classes of cosmic rays. AMS also found that the secondary cosmic rays
Li-Be-B and F-P-K belong to another two different classes of cosmic rays. The rigidity dependences of the secondary cosmic rays and
the primary cosmic rays are distinctly different. In particular, above GV the secondary cosmic rays harden twice as much as the primary
cosmic rays. The third group of cosmic rays N, Na, Al, Cl, Ar, and Ca can be described as linear combinations of primary (O, Si) and
secondary (B, F) cosmic rays. Compared with O and Si, the primary cosmic rays C, Ne, Mg, and S were found to have secondary
component, similar to N, Na, and Al. As a result, the C/O, N/O, Ne/Si, Na/Si, Mg/Si, Al/Si, S/Si, Cl/Si, Ar/Si, K/Si, and Ca/Si abundance
ratios at the source are directly determined independent of cosmic ray propagation. AMS found that the lightest and most abundant primary
proton cosmic rays have two components. Measuring the light isotopes, we found that D flux can also be described as a linear combination
of primary (He) and secondary (He) cosmic ray fluxes.

Speaker: vitali choutko (MIT)

239 Highlights from the AMS Experiment (2): Properties of Elementary Fluxes in Primary Cosmic Rays

Latest results by AMS on the fluxes and flux ratios of charged elementary particles in the absolute rigidity range from 1 up to 2000 GV
reveal unique properties of cosmic charged elementary particles. The positron flux in the TeV region exhibits complex energy dependence.
It is described by the sum of a term associated with the positrons produced in the collision of cosmic rays, which dominates at low energies,
and a new source term, which dominates at high energies and is associated with either dark matter or astrophysical origin. The existence of
this term is established with 5σ significance. The positron source term also manifest itself in the measured electron spectrum. This is the
first indication of the existence of identical charge symmetric source term both in the positron and in the electron spectra and, as a
consequence, the existence of new physics. The positron-to-antiproton flux ratio is independent of energy and its value is determined to be
a factor of 2 with percent accuracy in the energy range from ~60 to ~500 GeV This unexpected observation indicates a common origin
of high energy antiprotons and positrons in the cosmos.

Speaker: Weiwei Xu (Shandong Institute of Advanced Technology)

240 Highlights from the AMS Experiment: Precision measurements the hourly, daily, monthly, and yearly cosmic radiation over an 11-year solar cycle

The Alpha Magnetic Spectrometer (AMS-02) is a high-energy particle detector designed to measure different species of galactic cosmic rays in the GV to TV rigidity range with unprecedented accuracy, in order to study fundamental physics in space. Since its installation on the International Space Station in May 2011, AMS has been measuring hourly, daily, monthly, and yearly cosmic radiation over an 11-year solar cycle. The low-energy flux exhibits variations strongly related to solar activity. In addition, AMS-02 has measured Forbush decreases and solar energetic particles associated with the most intense solar events of solar cycle 24-25, during which radiation levels for manned space flight could easily reach the lethal dose of 300 rem. This unique information is vital for future human exploration of the Moon and Mars, and is different from current models used in calculations.

Speaker: Dimitrii Krasnopevtsev (Massachusetts Inst. of Technology (US))

241 Extending Cosmic-Ray Measurements over a Decade with CALET

The CALorimetric Electron Telescope (CALET) has been in operation on the International Space Station since October 2015, providing more than a decade of continuous and stable observations of high-energy cosmic rays and gamma rays. The mission aims to search for nearby cosmic-ray sources and dark matter signatures through precise measurements of cosmic-ray electrons, and to investigate cosmic-ray acceleration and propagation via measurements of the energy spectra of individual elements from protons to heavy nuclei. Over this extended observation period, CALET has revealed several notable features in cosmic-ray spectra. These include a spectral break around 1 TeV in the all-electron spectrum, as well as spectral hardening and softening in the TeV region for protons, helium, and heavier nuclei. The measured spectra extend toward the PeV scale. In this presentation, we summarize the latest CALET results based on more than a decade of observations, with an emphasis on high-energy spectral features and the long-term performance and stability of the detector in orbit.

Speaker: Yosui Akaike (Waseda University)

242 Probing Galactic Cosmic-Ray Propogation with HELIX

Highly energetic astrophysical processes are studied through measurements of cosmic radiation, yet the mechanisms responsible for accelerating particles to high energies remain unconfirmed. New isotope measurements of long-lived unstable nuclei can provide unique constraints on Galactic cosmic-ray propagation and the size of the Milky Way halo. In particular, the clock isotopes 10Be (radioactive, with a 1.4 Myr half-life) and 9Be (stable), offer a direct probe of these effects.

The High Energy Light Isotope eXperiment (HELIX) is a balloon-borne superconducting magnet spectrometer designed to measure abundances of light Galactic cosmic-ray isotopes from approximately 0.2 GeV/n to 10 GeV/n. HELIX adopts a staged approach to studying Galactic cosmic-ray propagation by directly measuring particle charge, magnetic rigidity, and velocity. Magnetic rigidity is measured with a high-precision drift chamber tracker inside a 1 T magnetic field, while charge and low-energy velocity are measured with time-of-flight scintillator paddles. At higher energies, velocity is measured with an aerogel-based ring-imaging Cherenkov detector.

HELIX completed a successful engineering flight from the Esrange Space Center in spring 2024, achieving approximately 6.3 days of flight time. Here, we present an overview of the payload, flight performance, the status of ongoing analysis, and preparation for future flights.

Speaker: Dennis Calderón (The Ohio State University)

243 From Atmospheric Muons to Prompt Neutrinos: Unfolding the Muon Flux in IceCube to Constrain Charm Production

At the highest energies, the prompt atmospheric neutrino flux from charmed-hadron decays contributes to the background in astrophysical neutrino source searches, but remains uncertain due to sparse constraints on forward heavy-flavor production and differences among hadronic interaction models. Atmospheric muons probe related air-shower physics and complement neutrino measurements: prompt neutrinos are dominated by charm decays, whereas prompt muons receive contributions from both charm and short-lived unflavoured mesons. Conventional muons from pion and kaon decays constrain light-meson production in air showers, which also governs the conventional atmospheric neutrino flux. We unfold the atmospheric muon flux in IceCube from sub-TeV to PeV energies using stopping and through-going muon samples. Improved machine-learning reconstructions and event selections enable a robust unfolding accounting for detector and ice systematic effects. We present the unfolded spectra, derive constraints on the prompt fraction in the atmospheric muon flux, and relate these results to prompt atmospheric neutrino expectations.

Speaker: Pascal Gutjahr (Adelaide University)

GR: GR8 : GRBs

244 Probing Microphysics of Gamma-Ray Burst Afterglow and X-ray Flares through Broadband X-ray to GeV Emission and Implications for Very-High-Energy Radiation.

Gamma-ray Bursts (GRBs) generate powerful relativistic jets that inject a large amount of energy into their surrounding environment, producing blast waves that accelerate particles to high energies. The GRB afterglow radiation provides a powerful means to investigate the microphysics of relativistic shocks and to probe the medium surrounding the progenitor of the burst. In this study, we present a comprehensive multiwavelength analysis of 31 GRBs observed between 2008 and 2024 from the Neil Gehrels Swift Observatory (X-ray Telescope and Burst Alert Telescope) and the Fermi Large Area Telescope, covering photon energies from 0.3 keV to 300 GeV. Our goal is to characterize the broadband spectral properties of GRB afterglows in soft X-rays, hard X-rays, and high-energy gamma rays. We investigate correlations between spectral shape and energy output across different parts of the spectrum. The observed emission is modeled using a forward shock scenario that includes both synchrotron and synchrotron self-Compton (SSC) radiation losses. The results favor an SSC-dominated radiation model in a wind- like medium, consistent with expectations for long-duration GRBs. Crucially, this work provides new benchmarks for the microphysical parameters governing the emission, particularly indicating a notably low magnetic energy fraction, which refines previous estimates. By modeling broadband data, this study offers one of the most detailed SSC analyses in a wind-like environment to date. Notably, our results naturally account for the comparable energy output observed in both the soft X-ray and TeV bands, consistent with the previously detected TeV-GRBs.

Moreover, the early X-ray afterglows of GRBs, observed with the Swift XRT, have revealed distinct temporal features such as X-ray flares beyond those predicted by the standard forward shock afterglow model. X-ray flares are commonly attributed to prolonged central engine activity, although their physical origin remains debated. In this talk, I will present a systematic multi-wavelength study of X-ray flares in a sample of 56 GRBs observed by the Swift XRT over 17 years, all located within the field of view of the Fermi LAT. The flares are classified into prompt, steep-decay, plateau, and afterglow categories based on their temporal behavior in the X-ray light curves. We found that only six events show significant high-energy emission (>3σ). However, detailed modeling indicates that the GeV high-energy emission is consistent with afterglow processes rather than flare-related processes. We explore correlations between spectral properties and energy output at 1 keV, 10 keV, and 1 GeV. The broadband emission is modeled within a forward-shock scenario including synchrotron self-Compton radiation. This framework allows us to constrain the underlying microphysical parameters governing the emission. Our results provide one of the most comprehensive analyses of X-ray flares to date. We also predict very-high-energy emission associated with flares and discuss detections with current and future very high-energy detectors, such as CTAO.

Speaker: Pawan Tiwari

245 The diversity of Einstein Probe gamma-ray bursts and associated transients: insights into jets and their environments

The Einstein Probe (EP), launched in 2024, was designed to explore the dynamic X-ray sky and advance our understanding of gamma-ray bursts (GRBs) and stellar explosions. With its sensitivity to soft X-rays and rapid localization capability, EP, together with extensive multi-wavelength follow-up campaigns, has uncovered a growing sample of GRB-related events. Observations from the earliest stages of these explosions have revealed a remarkable diversity of transients emerging on timescales of hours to weeks after the trigger, pointing to a wide range of jet properties, progenitor structures, and circumstellar environments. However, most of these events have been interpreted individually, and a global physical framework connecting them to one another and to the broader GRB population is still lacking. Here, we present a systematic analysis of the EP transient sample discovered to date within a unified theoretical framework that follows the interaction of relativistic jets with progenitor stars and surrounding circumstellar material. We show that much of the observed diversity can be understood through variations in a few key physical parameters: jet energy, extent of circumstellar material, and observer viewing angle. These parameters naturally produce on-axis jets, off-axis jets, and barely failed jets, giving rise to classical GRBs with bright afterglows, GRBs with initially rising afterglows, and soft GRBs accompanied by fast blue optical transients, respectively. This framework identifies the observational signatures of different jet outcomes and provides a physical basis for interpreting current EP discoveries and predicting future transients.

Speaker: Hamid Hamidani (Tohoku University)

246 Probing particle acceleration in Gamma-ray Burst afterglows through novel MeV correlation

The MeV afterglow in gamma-ray bursts (GRBs) represents a largely unexplored window into the transition from prompt emission to forward-shock-dominated afterglow. At MeV energies, the emission could arise from synchrotron radiation of the decelerating forward shock or from lingering prompt emission components. Each of these mechanisms carries distinct signatures of jet physics, magnetic field structure, and central engine behaviour. Therefore, disentangling these mechanisms is critical, yet capturing the MeV emission from slowly varying transients after the prompt emission (after T90) is challenging as MeV instruments are typically background-dominated. While Swift-BAT is sensitive to early afterglow emission, it detects only a fraction (typically 35%) of GRBs observed by Fermi-GBM. The broader detection rate and hard X-ray coverage of Fermi-GBM make it a powerful tool for probing MeV emission beyond T90. In our work, we applied a novel method of extracting the MeV afterglow from GBM-detected bursts using orbital background subtraction. This allows us to capture the faint MeV emission from GRBs beyond the prompt emission phase, which cannot be recovered via conventional analysis techniques. Applying this technique to a sample of the ~20 most fluent GRBs from 18 years of Fermi-GBM observations, we systematically characterise the spectral and temporal properties. Tracking the spectral index evolution across our sample reveals changing radiative processes that govern the prompt-to-afterglow transition.

In my presentation, I’ll discuss these findings, which also have direct implications for TeV studies of GRBs, as understanding the MeV afterglow and particle acceleration processes provides crucial constraints on the origin and evolution of very-high-energy (TeV) emission.

Speaker: Shraddha Mohnani (Indian Institute Of Technology Indore)

247 GRB 260226A: An Exceptionally Bright Gamma-Ray Burst Observed by Fermi-GBM and LAT

On 2026 February 26 at 10:37:55 UTC, the Fermi Gamma-ray Burst Monitor (GBM) triggered on the exceptionally bright, long-duration GRB 260226A. Owing to its extreme intensity, the burst also triggered the Large Area Telescope (LAT) onboard approximately 20 s later, marking only the second time during the Fermi mission that an autonomous onboard trigger was initiated from a LAT seed localization. The burst was observed by several missions in the hard X-ray/gamma-ray band, however, no optical or radio counterpart was identified. Ground-based imaging atmospheric Cherenkov telescopes were unable to observe the event because of Moon constraints, while other space-based follow-up opportunities were limited by operational or Sun-angle constraints, leaving the redshift unknown.

The LAT observations reveal one of the brightest bursts detected by the instrument, with a Test Statistic exceeding 3000 over the first 1500 s after trigger and more than 600 significant photons (above 100 MeV) detected. Remarkably, despite the burst brightness, the highest-energy LAT photon was only 1.1 GeV, arriving at T0 + 420 s. GRB 260226A also establishes a new record in LAT Low Energy (LLE) data, reaching a significance of 75.3σ. No evidence of detector saturation or pile-up is found in either GBM or LAT data.

A pronounced dip is observed in both the GBM light curve (around T0 + 25 s) and the LLE emission (around T0 + 23 s), potentially signaling the onset of afterglow emission while prompt activity was still ongoing. Joint time-integrated and time-resolved spectral analysis of GBM, LLE, and LAT data further reveals a persistent spectral cutoff at energies of tens of MeV throughout the main emission episode, placing constraints on the bulk Lorentz factor and opacity of the outflow. We present the temporal and spectral properties of this extraordinary event and discuss their implications for prompt and early afterglow emission mechanisms.

Speaker: Niccolo' Di Lalla (Stanford University)

248 Predicting Multiwavelength Emission Associated with X-Ray Flares and Extended Emission of Gamma-Ray Bursts

Gamma-ray bursts (GRBs) are among the most extreme transients in the universe, but their explosion and emission mechanisms remain unclear. To investigate the nature of GRB jets, we focus on X-ray flares (XFs) and extended emissions (EEs), which are X-ray emissions occurring 100 to 1000 seconds after the main burst. These signals can be observed with recently developed multi-wavelength facilities. In this study, we calculate the associated multi-wavelength emissions from XFs and EEs under the hypothesis that they arise from optically thin synchrotron emission by nonthermal electrons in relativistic jets. By considering ranges of the dissipation radius, $r_{\rm diss}$, and the jet Lorentz factor, $\Gamma$, we determine the parameter space in which detectable emission can be produced at each wavelength. We find that simultaneous ultraviolet and very-high-energy gamma-ray emission associated with XFs or EEs can be detected by Swift/UVOT, SVOM/VT, and CTAO approximately once every three years. The detection and non-detection rates for each detector provide key constraints on uncertain but essential parameters for understanding the physics of GRB jets.

Speaker: Riki Matsui

MM: MM8 : AGNs

249 Revisiting Disk Winds in Active Galactic Nuclei as an Origin of Cosmic Gamma-ray and Neutrino Backgrounds

The origins of the cosmic neutrino background (CNB) and the cosmic gamma-ray background (CGB) remain uncertain. Accretion disk winds driven by active galactic nuclei (AGNs) have been proposed as possible contributors, but the background contribution they are predicted to make depends sensitively on poorly constrained wind energetics and ambient densities. In this contribution, I will revisit the AGN disk-wind scenario by constructing a lepto-hadronic wind model calibrated against radio and GeV gamma-ray fluxes of nearby Fermi-LAT-detected Seyfert galaxies. In this framework, cosmic rays are accelerated at both the wind-driven forward and reverse shocks, and then produce synchrotron, external Compton, and hadronic gamma-ray emission. Applying our calibrated lepto-hadronic models to an AGN population synthesis model, we find that disk winds contribute at most $\lesssim 5\%$ of the CGB above 10 GeV and $\lesssim 10\%$ of the CNB around 100 TeV.

Speaker: Nobuyuki Sakai (The University of Osaka)

250 Toward a Self Consistent Contribution of Supermassive Black Hole X-ray Coronae to the Diffuse Extragalactic Neutrino Background

We present a generalized neutrino luminosity function for protons accelerated in the X-ray coronae of supermassive black holes in Seyfert-like galaxies. A major uncertainty in assessing the diffuse neutrino contribution of these systems is the underlying particle acceleration physics. We address this using a theoretical acceleration framework informed by plasma kinetic simulations, enabling a more self-consistent connection between coronal conditions, nonthermal proton populations, and neutrino production. In this picture, the neutrino luminosity depends primarily on the coronal X-ray luminosity and magnetization, and only weakly on black hole mass. We find that the cosmologically integrated emission from these systems can account for the sub-PeV diffuse extragalactic neutrino flux observed by IceCube. We further argue that, although diffusive confinement is relatively well understood, the magnetic field topology near black holes naturally allows for cosmic ray-driven outflows near the X-ray corona. Such outflows may accompany efficient neutrino production and influence the dynamics of the innermost galactic environment.

Speaker: Rostom Mbarek (Princeton University)

251 Turbulent AGN coronae as the origin of diffuse neutrinos up to PeV energies

It has been shown that the turbulence acceleration in AGN coronae can account for 1-10 TeV neutrinos from some AGNs, such as the Seyfert galaxy NGC 1068. Based on this, there are attempts to explain the diffuse neutrinos observed by IceCube with the accumulated contribution from a population of AGNs, but it is found that the maximum neutrino energy is less than tens of TeV and, as a result, additional source classes are needed to explain the high-energy component above this energy. Recently, motivated by the detection of $>100$ TeV neutrinos from the Seyfert galaxy NGC 7469, it was shown that the turbulence acceleration in the corona can explain $>$100 TeV neutrinos given a larger magnetization parameter ($\sigma\sim 1$) in the corona, which leads to a larger maximum proton energy and a hard proton spectrum. In this paper, we extend this assumption to the population of AGNs and study whether the population of AGNs with a wide range of magnetization can explain the entire diffuse neutrino flux. We find that AGN coronae could account for the diffuse neutrinos up to PeV energies if a significant fraction of AGNs have magnetizations as large as $\sigma\sim 1-10$. This conclusion is insensitive to the shape of the magnetization parameter distribution as long as the range of the magnetization parameter is sufficiently wide and the distribution is flat towards high magnetization. Interestingly, this model can also explain the peak of the diffuse neutrino spectrum at $\sim30$ TeV.

Speaker: Qi-rui Yang (Nanjing University)

252 Multi-Instrument, Multi-Messenger Blazar Modelling

Blazars, a subclass of jetted active galactic nuclei, provide exceptional laboratories for astrophysical particle acceleration processes. These extreme environments have proven difficult to model in their entirety, even with multiwavelength datasets spanning from radio waves to gamma-rays. One major point of contention is the particle composition of the jet, with the main contenders being either leptonic or lepto-hadronic plasmas. While the presence of leptons is accepted to be the origin of the lower energy parts of the emission spectra, the higher energies (x-rays to gamma-rays) can pose problems to purely leptonic scenarios. While the presence of neutrinos emitted from these jets would be definitive evidence of a hadronic component, their widespread detection from blazars remains elusive.

Recent work on the Gammapy Python package allows for the fitting of multi-wavelength data over multiple energy decades simultaneously. In the work presented, we have coupled the B13 lepto-hadronic code to the Gammapy framework, allowing for multiwavelength fitting. In addition, we have characterised the IceCube detector within the aforementioned framework, based on effective area and smearing files from the public data release “All-sky point-source IceCube data: years 2008-2018”. This permits not only the fitting of models to multi-instrument data, but also the constraining of the parameter space available based on neutrino output (or lack thereof).

Speaker: Joshua Robinson (North-West University)

253 Search for neutrinos from optically-identified AGNs with IceCube

Recent IceCube measurements have identified the central regions of active galactic nuclei (AGN) as promising sites for cosmic-ray acceleration, largely through correlation studies with X-ray bright sources. Since X-ray emission is typically dominated by the AGN over the host galaxy, it serves as a robust proxy of the central activity correlated with the expected neutrino flux. Previous IceCube studies have often relied on AGNs detected by the wide-field hard X-ray satellite Swift-BAT; however, its sub-degree PSF can lead to contamination from broader components such as AGN jets and star-forming activities. To mitigate this effect, optical emission lines can be alternatively used to identify and quantify the intrinsic AGN activities. In this presentation, we will present a new high-statistics catalog of AGN samples extracted from two large optical spectroscopy catalogs, SDSS and DESI, using the emission line fluxes. Then, we will discuss the progress of the correlation study with the latest IceCube neutrino dataset.

Speaker: Satoshi Fukami (DESY)

254 On the origin of delayed radio flares in neutrino-associated blazars: the case of TXS 0506+056

Radio flares have been proposed as possible signatures of astrophysical neutrino production. In TXS 0506+056, the 2017 IceCube-170922A /$gamma$-ray flare was followed by a GHz radio maximum roughly 2–3 years later. We investigate whether this delayed radio flare can be explained by the same compact region that produced the neutrinos and $gamma$-rays, as it expands downstream and becomes less affected by synchrotron self-absorption. Using LeHaMoC code in a fully time-dependent framework, we model the evolution of the emitting region starting from the 2017 flare parameters and compare the predicted 1.2–22 GHz light curves with RATAN-600 data. We study different scenarios with increasing levels of sophistication, including continuous injection and energy re-dissipation to particles on parsec scales. We find that a simple expanding-blob model cannot reproduce the observed radio behavior. Instead, the data are better explained by a downstream re-dissipation episode in the optically thin regime, followed by jet deceleration. In our one-zone framework, the delayed radio flare is therefore unlikely to result from a neutrino-production region that becomes radio-transparent. Rather, it appears to reflect downstream dissipation and changes in relativistic beaming. Because the radio flare is powered mainly by leptonic synchrotron emission and is largely insensitive to the proton population, it should not be regarded as a direct tracer of neutrino production.

Speaker: Stamatios Ilias Stathopoulos (DESY)

255 Little Red Dots as Hidden Neutrino Sources

Little Red Dots (LRDs) are enigmatic, compact, red galaxies at high redshift, z ∼ 4–7, discovered by the James Webb Space Telescope. Broad emission lines in the absence of X-ray and radio counterparts suggest that they host accreting supermassive black holes embedded in dense gaseous envelopes. This black-hole-envelope configuration facilitates efficient photohadronic interactions and neutrino production. Remarkably, their observed source number density and luminosity are compatible with the energetics of the diffuse neutrino background. We consider that relativistic jets and outflows are launched from the black hole and propagate through low-density polar funnels within envelopes, where particle acceleration and neutrino emission occur. This leads to LRDs being effectively hidden sources. Our analytic and numerical calculations show that, in an optimistic scenario, LRDs can contribute ∼ 30% of the observed diffuse background at TeV–sub-PeV energies, predominantly through photomeson production. At high neutrino energies, $\gtrsim 10^{5.5}$ GeV, inverse Compton cooling of muons modifies the resulting flavor ratio, providing a distinctive diagnostic for IceCube–Gen2 and other upcoming neutrino telescopes.

Speaker: Riku Kuze (Yukawa Institute for Theoretical Physics)

7:00 PM banquet

Friday, September 4

Plenary

256 X-ray observation campaigns of Galactic PeVatron candidates

The origin of Galactic cosmic rays (CRs) above the PeV scale, particularly around the knee of the all-particle spectrum, remains a fundamental open question in high-energy astrophysics. Recent developments of air shower arrays, such as Tibet AS$\gamma$, HAWC, and LHAASO, opened up a new era by detecting ultra-high-energy (UHE; E>100 TeV) gamma rays. These UHE sources are possible candidates of PeV cosmic-ray accelerators $-$ PeVatrons. The number of the UHE sources is increasing and currently stands at approximately 50. The identified dominant source type is related to pulsars, pulsar wind nebulae (PWNe), and their halos. The most growing population is microquasars $-$ X-ray binaries hosting a black hole or neutron star with (semi-)relativistic jets. Remarkably, half of the UHE sources remain unidentified mainly because of lacking observations at different wavelengths.

These UHE detections have triggered extensive multiwavelength follow-up campaigns to investigate the origin of gamma rays and unveil the underlying mechanism of particle acceleration. Indeed, our XMM-Newton observations revealed new X-ray extended sources in, e.g., an unidentified source LHAASO J0341+5258 and a microquasar V4641 Sgr, which are plausible counterparts of a PWN and a microquasar lobe, respectively.

In this talk, I will present an overview of our X-ray observation campaigns of the UHE sources, including microquasars SS 433/W50 and V4641 Sgr and several unidentified LHAASO sources.

Speaker: Naomi Tsuji (ICRR, The University of Toko)

257 New Physics with Cosmic Rays and Neutrinos

Cosmic rays and neutrinos provide access to particle interactions at energies and densities beyond the reach of terrestrial experiments. Combined with gamma rays, they offer a multimessenger view of extreme astrophysical environments and a window onto relics from the early Universe. Here I will discuss how these messengers can be used to search for new physics, with emphasis on the cosmic neutrino background, dark matter, and other beyond the Standard Model phenomena. I will emphasize that the power of the multimessenger approach lies in its ability to disentangle new physics signals from astrophysical backgrounds, a key step toward any robust detection.

Speaker: GONZALO HERRERA (MIT, Harvard)

258 Gravitational-wave searches independent of LIGO-Virgo-KAGRA

Gravitational-wave astronomy has transitioned from a era of first discoveries to a high-throughput discipline, providing an unprecedented look at the population of merging compact objects like black holes and neutron stars. I will highlight recent advances in gravitational-wave searches that exploit the richer signal structure predicted by General Relativity to significantly boost the overall detection sensitivity for these rare systems, with the largest gains for binaries with unequal masses and tilted orbits. I will then discuss what the larger catalogs reveal about the distributions and assembly histories of merging compact objects, and how these observations constrain their broader astrophysical and cosmological contexts.

Speaker: Tejaswi Venumadhav Nerella (University of California Santa Barbara)

11:00 AM break

Plenary

259 Toward identifying ultra-high-energy cosmic ray sources with improved magnetic field modeling

Ultra-high-energy cosmic rays (UHECRs) are the most energetic particles known - and yet their origin is still an open question. However, with the precision and accumulated statistics of the Pierre Auger Observatory and the Telescope Array, in combination with advancements in theory and modeling - especially of the Galactic magnetic field - it is now possible to set solid constraints on the sources of UHECRs. The spectrum and composition measurements above the ankle can be well described by a population of extragalactic, homogeneously distributed sources. Using additionally the observed anisotropy in the arrival directions, namely the large-scale anisotropies as well as smaller-scale warmspots at higher energies, even more powerful constraints on the source density as well as the contribution of individual sources can be placed. However, these findings raise further questions, for example whether sources are transient or continuous or why sources are required to be strikingly similar to explain the measurements. The current findings and possible interpretation of UHECR data will be presented in this review.

Speaker: Teresa Bister (Nikhef / Radboud University)

260 Beyond Standard Misalignment: Theory of Axion and ALP Dark Matter

Axions and axion-like particles are well-motivated dark matter candidates whose relic abundance is often attributed to the standard misalignment mechanism. After briefly reviewing the conventional picture, I will discuss several non-minimal realizations of axion dark matter, including trapped misalignment, bubble misalignment, and level crossing in multi-axion systems, which can qualitatively alter the production and distribution of dark matter.

Speaker: Fuminobu Takahashi (Tohoku University)

261 Hidden engines in core-collapse supernovae: multi-messenger signatures of choked jets

Core-collapse supernovae (CCSNe) are promising multi-messenger sources, potentially emitting neutrinos and electromagnetic radiation across a wide range of timescales and energies. For very extended stellar envelopes, relativistic jets launched in the explosion may fail to escape the progenitor star, forming so-called choked jets. While these systems are invisible in gamma rays, they can be sites of particle acceleration and may contribute to the diffuse high-energy neutrino flux observed by IceCube. They can also produce early ultraviolet and optical emission through jet–ejecta and circumstellar interactions, offering complementary probes of the early explosion dynamics.
In this talk, I will present a multi-messenger perspective on CCSNe focused on these hidden jet-driven events, and discuss how neutrinos and early electromagnetic signals can be combined to uncover otherwise obscured explosions. I will outline observational strategies that connect wide-field transient surveys with neutrino detectors. I will also highlight recent progress in the theoretical and numerical modeling of these systems. These efforts aim to assess whether choked jets are efficient sites of particle acceleration and to derive more robust predictions for their electromagnetic signatures in these stellar environments.

Speaker: Angela Zegarelli (Ruhr University Bochum)

Farewell