Probing the evolution of the EAS muon content in the atmosphere with KASCADE-Grande

TL;DR

This study investigates the muon content evolution in high-energy air showers using KASCADE-Grande data, revealing discrepancies with existing hadronic interaction models, especially regarding muon attenuation and zenith angle evolution.

Contribution

It provides the first measurement of muon attenuation length in the atmosphere for energies between 10^{16.3} and 10^{17.0} eV and compares these with multiple models, highlighting their limitations.

Findings

Muon attenuation length measured as 1256 g/cm^2.

All models underestimate muon attenuation compared to data.

Models fail to accurately describe zenith angle evolution of muon content.

Abstract

The evolution of the muon content of very high energy air showers (EAS) in the atmosphere is investigated with data of the KASCADE-Grande observatory. For this purpose, the muon attenuation length in the atmosphere is obtained to $\Lambda_\mu = 1256 \, \pm 85 \, ^{+229}_{-232}(\mbox{syst})\, \mbox{g/cm}^2$ from the experimental data for shower energies between $10^{16.3}$ and $10^{17.0} \, \mbox{eV}$. Comparison of this quantity with predictions of the high-energy hadronic interaction models QGSJET-II-02, SIBYLL 2.1, QGSJET-II-04 and EPOS-LHC reveals that the attenuation of the muon content of measured EAS in the atmosphere is lower than predicted. Deviations are, however, less significant with the post-LHC models. The presence of such deviations seems to be related to a difference between the simulated and the measured zenith angle evolutions of the lateral muon density distributions of EAS, which also causes a discrepancy between the measured absorption lengths of the density of shower muons and the predicted ones at large distances from the EAS core. The studied deficiencies show that all four considered hadronic interaction models fail to describe consistently the zenith angle evolution of the muon content of EAS in the aforesaid energy regime.