Update on the Combined Analysis of Muon Measurements from Nine Air Shower Experiments

TL;DR

This paper updates a meta-analysis of muon measurements from nine air shower experiments, revealing a consistent muon excess over simulations that grows with energy, highlighting discrepancies in hadronic interaction models at ultra-high energies.

Contribution

It provides a comprehensive update on muon density measurements across multiple experiments, standardizing data comparison and analyzing muon excess trends at energies above 10 PeV.

Findings

Muon excess increases with energy above 10 PeV.

Discrepancies are consistent across different hadronic models.

The significance of the muon excess slope is analyzed in detail.

Abstract

Over the last two decades, various experiments have measured muon densities in extensive air showers over several orders of magnitude in primary energy. While some experiments observed differences in the muon densities between simulated and experimentally measured air showers, others reported no discrepancies. We will present an update of the meta-analysis of muon measurements from nine air shower experiments, covering shower energies between a few PeV and tens of EeV and muon threshold energies from a few 100 MeV to about 10 GeV. In order to compare measurements from different experiments, their energy scale was cross-calibrated and the experimental data has been compared using a universal reference scale based on air shower simulations. Above 10 PeV, we find a muon excess with respect to simulations for all hadronic interaction models, which is increasing with shower energy. For EPOS-LHC and QGSJet-II.04 the significance of the slope of the increase is analyzed in detail under different assumptions of the individual experimental uncertainties.