2024/10/30 by G. Di Sciascio, Di Sciascio, Giuseppe
Physics and Astronomy · #FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE) #High Energy Physics - Experiment (hep-ex) #High-Energy Particle Collisions Research #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions
paper · pdf · doi:10.48550/arxiv.2410.22974
openalex publication_date 2024/10/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
In high energy Gamma-Ray Astronomy with shower arrays the most discriminating signature of the photon-induced showers against the background of hadron-induced cosmic-ray is the content of muons in the observed events. In the electromagnetic γ-showers the muon production is mainly due to the photo-production of pions followed by the decay π→μν. In high energy photo-production process the photon exhibits an internal structure which is very similar to that of hadrons. Indeed, photon-hadron interactions can be understood if the physical photon is viewed as a superposition of a bare photon and an accompanying small hadronic component which feels conventional hadronic interactions. Information on photo-production γp and γγ cross-sections are limited to √(s)≤ 200 GeV from data collected at HERA. Starting from Elab≈100 TeV the difference between different extrapolations of the cross sections increases to more than 50% at Elab≈1019 eV, with important impact on a number of shower observables and on the selection of the photon-initiated air showers. Recently, the LHAASO experiment opened the PeV-sky to observations detecting 40 PeVatrons in a background-free regime starting from about Elab≈ 100 TeV. This result provides a beam of pure high energy primary photons allowing to measure for the first time the photo-production cross section even at energies not explored yet. The future air shower array SWGO in the Southern Hemisphere, where the existence of Super-Pevatrons emitting photons well above the PeV is expected, could extend the study of the hadron nature of the photons in the PeV region. In this contribution the opportunity for a measurement of the photo-production cross section with air shower arrays is presented and discussed.