Forward hadron production in proton-air collisions above LHC energies through the fluctuations of extensive air showers

TL;DR

This paper demonstrates that fluctuations in extensive air showers caused by ultra-high-energy proton-air collisions can serve as a new probe for hadronic physics beyond current accelerator capabilities, with smaller uncertainties than existing models.

Contribution

It introduces a probabilistic framework to analyze shower fluctuations, isolating initial collision physics from subsequent shower development, providing a novel method to study hadron production at extreme energies.

Findings

Fluctuations in shower maximum and muon content reveal initial collision physics.

The method reduces uncertainties compared to current hadronic interaction models.

Provides a new observational approach for ultra-high-energy hadronic interactions.

Abstract

Primary proton-air interactions at ultra-high energies leave a physically interpretable imprint on the correlated fluctuations of the depth of shower maximum and the muon content in extensive air showers. This imprint reflects the stochasticity in the partition of the primary energy among secondary particles in the first interaction. We show that these fluctuations can be accessed through a probabilistic description that isolates sensitivity to hadronic physics in the initial collision, while treating the subsequent shower development as effectively universal. The uncertainties resulting from this universality are smaller than the spread among current hadronic interaction models and comparable to current experimental uncertainties. Consequently, the joint observable space defined by these two quantities provides a new probe of hadron production in kinematic regimes far beyond the reach of human-made accelerators.