2026/07/24 by The Pierre Auger Collaboration, A. Abdul Halim, P. Abreu +347
#hep-ex #astro-ph.HE
Hybrid measurements at the Pierre Auger Observatory indicate that most high-energy hadronic interaction models underestimate the average depth of the shower maximum, ⟨ Xmax ⟩, at a center-of-mass energy of √(s)=97.7 ± 0.4+6.6-6.2 TeV. In this Letter, the hadronic interaction models are shown to follow a universal relation between the predicted ⟨ Xmax ⟩ and the mean values of variables characterizing the energy spectra of secondary particles produced in the first interaction of proton-induced air showers. Assuming the validity of these relations in Nature, we map the values of ⟨ Xmax ⟩ favored by Auger data into mean values of these variables. All models favor an increase in the mean elasticity and in the fraction of hadronic energy in proton--air interactions. The latter must be amplified by a factor of 2.8 to 4.6 to account for the muon puzzle.