Speaker
Description
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.
