Tests of hadronic interactions using the Pierre Auger Observatory

S. J. SCIUTTO; P. HANSEN; THE PIERRE AUGER COLLABORATION.

Seúl

Conferencia; The 39th International Conference on High Energy Physics (ICHEP2018); 2018

The International Union of Pure and Applied Physics

Ultra-high energy cosmic rays (UHECR) can be used to study hadronic interactions beyond LHCenergies. In this contribution, we summarize relevant data from the Pierre Auger Observatory.While the proton-air cross section has been measured atps = 57 TeV and found to be in goodagreement with extrapolations from LHC energies, other observables are significantly differentfrom what is predicted using current models. In particular, the predictions from models of showersbased on LHC data are in strong contradiction with the observed number of muons. More muonsare detected than predicted with the magnitude of the effect being model-dependent. Anotherobservable from the Pierre Auger Observatory, the distribution of the depths of muon production,is also poorly described. Indeed no current model is capable of describing the full range of datafrom the Observatory, thus highlighting deficiencies in extrapolations beyond LHC energies. Thediscrepancy between hadronic models can be examined further by measuring separately the muonand electromagnetic components of the signal recorded by detectors on the ground. The PierreAuger Observatory is being upgraded by the addition of plastic scintillator detectors above thewater-Cherenkov detectors to achieve this. The new observations will enable rigorous testing ofhadronic models up tops 100 TeV and are crucial to the quest of determining the compositionof UHECR.