Speaker
Description
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.
