New physics Air-Shower simulations for UHECR above 50 TeV

Discussion timeslot (ZOOM-Meeting): 14. July 2021 - 18:00
ZOOM-Meeting URL: https://desy.zoom.us/j/92210078166
ZOOM-Meeting ID: 92210078166
ZOOM-Meeting Passcode: ICRC2021
Corresponding Session: https://icrc2021-venue.desy.de/channel/03-Muon-Puzzle-and-EAS-modeling-CRI/110
Live-Stream URL: https://icrc2021-venue.desy.de/livestream/Discussion-03/4

Abstract:
'The average shower depth <X_max> of Ultra-high Energy Cosmic Rays is observed to flatten with energy at the highest energies. The standard interpretation of these data is that the composition is getting heavier; an alternative interpretation is the existence of new effects in proton interactions above ~50 TeV center-of-mass energy. We have used CORSIKA to study, through air-shower simulations, observational signatures of a possible increase in cross-section and multiplicity in collisions exceeding this threshold. We have simulated hadronic collisions for primaries with energies in the range 10^8 - 10^11 GeV. We have used two different high energy models for the simulations, QGSJETII-04 and EPOSLHC, with Fluka for low energy interactions on both. A smooth transition from Galactic to extragalactic cosmic rays was implemented, by fitting a Galactic component with an exponential suppression at ~10^9 GeV. The remaining flux in Auger data was interpreted as extragalactic protons. Above 10^9 GeV, the proton-air cross-section and the multiplicity of secondary particles were altered, so as to bring the simulated <X_max> in agreement with Auger data. The parameter space of the viable cross-section and multiplicity in the scenario where the composition of Auger cosmic rays at the highest energies remains unchanged and light, places constraints on the phenomenology of any new physics affecting the interactions for high energy protons that may be probed by sqrt{s}>50 TeV collisions. We found out that if new physics indeed sets in, the cross-section of proton-Air interactions has to be ~ 800-900 mb at 140 TeV center-of-mass energy, accompanied with an increase of the number of secondary particles by a factor between 2-3.'

Authors: Stylianos Romanopoulos | Vasiliki Pavlidou | Theodore Tomaras
Indico-ID: 1170
Proceeding URL: https://pos.sissa.it/395/475