Speaker
Description
Arrays of Imaging Atmospheric Cherenkov Telescopes (IACTs), like the High Energy Stereoscopic System (H.E.S.S.), observe extensive air showers initiated by gamma rays and cosmic rays when interacting with the Earth’s atmosphere. IACTs image the distribution of Cherenkov light emitted by air shower particles as they propagate through Earth's atmosphere. The traditional reconstruction of gamma-ray showers relies on the Hillas parameterization, which employs elliptical image modeling to narrow down the measurement to a few characteristics.
For the analysis of cosmic rays, which are usually considered background in gamma-ray astronomy, the reconstruction is more challenging. Since the development of hadronic showers is subject to larger fluctuations, the detected images feature deviations from the typical elliptical shape, making modifications necessary.
In this contribution, we adapt the Hillas parametrization to enable a precise reconstruction of proton showers using the H.E.S.S. array. After applying the modified reconstruction, we use offruns to derive the proton spectrum between 4 and 200 TeV. We find evidence for a break of the spectral index, which matches well previous space-based experiments, confirming for the first time a change in the proton spectrum using IACT arrays. Finally, we discuss systematic uncertainties and outline analysis improvements by utilizing machine learning.
