Testing Hadronic Interactions at Ultrahigh Energies with Air Showers Measured by the Pierre Auger Observatory

TL;DR

This paper introduces a new method to test hadronic interaction models at ultrahigh energies using air shower data from the Pierre Auger Observatory, revealing significant muon excesses compared to model predictions.

Contribution

A novel approach to test hadronic models without relying on absolute energy calibration, applied to ultra-high-energy cosmic ray air showers.

Findings

Average hadronic shower size exceeds model predictions by 33-61%.

Detected muon excess indicates discrepancies in current hadronic interaction models.

Method enables testing of particle physics at energies beyond current accelerators.

Abstract

Ultrahigh energy cosmic ray air showers probe particle physics at energies beyond the reach of accelerators. Here we introduce a new method to test hadronic interaction models without relying on the absolute energy calibration, and apply it to events with primary energy 6-16 EeV (E_CM = 110-170 TeV), whose longitudinal development and lateral distribution were simultaneously measured by the Pierre Auger Observatory. The average hadronic shower is 1.33 +- 0.16 (1.61 +- 0.21) times larger than predicted using the leading LHC-tuned models EPOS-LHC (QGSJetII-04), with a corresponding excess of muons.