# Through the Looking-Glass with ALICE into the Quark-Gluon Plasma: A New Test for Hadronic Interaction Models Used in Air Shower Simulations

## TL;DR

This paper proposes a new test for hadronic interaction models based on ALICE's observations of strangeness enhancement, revealing that current models need retuning to accurately simulate ultra-high-energy cosmic-ray air collisions.

## Contribution

It introduces a novel test for hadronic models using ALICE's strangeness data, highlighting the need for retuning of QCD Monte Carlo codes for cosmic-ray simulations.

## Key findings

- Current models do not reproduce the strangeness enhancement observed by ALICE.
- Retuning of hadronic interaction models is necessary for accurate UHECR air shower simulations.
- The test links LHC heavy-ion results to cosmic-ray physics, providing a new validation method.

## Abstract

Recently, the ALICE Collaboration reported an enhancement of the yield ratio of strange and multi-strange hadrons to charged pions as a function of multiplicity at mid-rapidity in proton-proton, proton-lead, lead-lead, and xenon-xenon scattering. ALICE observations provide a strong indication that a quark-gluon plasma is partly formed in high multiplicity events of both small and large colliding systems. Motivated by ALICE's results, we propose a new test for hadronic interaction models used for analyzing ultra-high-energy-cosmic-ray (UHECR) collisions with air nuclei. The test is grounded in the almost equal column-energy density in UHECR-air collisions and lead-lead collisions at the LHC. We applied the test to post-LHC event generators describing hadronic phenomena of UHECR scattering and show that these QCD Monte Carlo-based codes must be retuned to accommodate the strangeness enhancement relative to pions observed in LHC data.