# Measurements and tests of hadronic interactions at ultra-high energies with the Pierre Auger Observatory

## TL;DR

This paper reports measurements of hadronic interactions at energies beyond current accelerators using the Pierre Auger Observatory, revealing good agreement in electromagnetic components but discrepancies in muon-related observables.

## Contribution

It provides the first measurements of proton-air cross sections at 39 and 56 TeV and compares hadronic models with extensive air shower data at ultra-high energies.

## Key findings

- Proton-air cross sections measured at 39 and 56 TeV.
- Good agreement between models and electromagnetic shower data.
- Discrepancies observed in muon-related observables.

## Abstract

Extensive air showers are complex objects, resulting of billions of particle reactions initiated by single cosmic ray at ultra-high-energy. Their characteristics are sensitive both to the mass of the primary cosmic ray and to the details of hadronic interactions. Many of the interactions that determine the shower features occur in kinematic regions and at energies beyond those tested by human-made accelerators. We will report on the measurement of the proton-air cross section for particle production at a center-of-mass energy per nucleon of 39 TeV and 56 TeV. We will also show comparisons of post-LHC hadronic interaction models with shower data by studying the moments of the distribution of the depth of the electromagnetic maximum, the number and production depth of muons in air showers, and finally a parameter based on the rise-time of the surface detector signal, sensitive to the electromagnetic and muonic component of the shower. While there is good agreement found for observables based on the electromagnetic shower component, discrepancies are observed for muon-sensitive quantities.