Investigating Hadronic Interactions at Ultra-High Energies with the Pierre Auger Observatory

TL;DR

This paper discusses how the Pierre Auger Observatory measures extensive air showers to study hadronic interactions at energies beyond current accelerators, testing and constraining models of ultra-high-energy cosmic rays.

Contribution

It introduces methods to analyze air shower observables for probing hadronic interactions at ultra-high energies and evaluates the consistency of hadronic models with observational data.

Findings

Assessment of hadronic cross-sections from shower profiles

Measurement of muon content and fluctuations

Testing of hadronic interaction models against data

Abstract

The development of an extensive air shower depends not only on the nature of the primary ultra-high-energy cosmic ray but also on the properties of the hadronic interactions. For energies above those achievable in human-made accelerators, hadronic interactions are only accessible through the studies of extensive air showers, which can be measured at the Pierre Auger Observatory. With its hybrid detector design, the Pierre Auger Observatory measures both the longitudinal development of showers in the atmosphere and the lateral distribution of particles that arrive at the ground. This way, observables that are sensitive to hadronic interactions at ultra-high energies can be obtained. While the hadronic interaction cross-section can be assessed from the longitudinal profiles, the number of muons and their fluctuations measured with the ground detectors are linked to other physical properties. In addition to these direct studies, we discuss here how measurements of the atmospheric depth of the maximum of air-shower profiles and the characteristics of the muon signal at the ground can be used to test the self-consistency of the post-LHC hadronic models.