On the model uncertainties for the predicted muon content of extensive air showers

Abstract

Motivated by the excess of the muon content of cosmic ray induced extensive air showers (EAS), relative to EAS modeling, observed by the Pierre Auger Observatory, and by the tension between Auger data and air shower simulations on the maximal muon production depth $X_{max}^{\mu }$, we investigate the possibility to modify the corresponding EAS simulation results, within the Standard Model of particle physics. We start by specifying the kinematic range for secondary hadron production, which is of relevance for such predictions. We further investigate the impact on the predicted EAS muon number and on $X_{max}^{\mu }$ of various modifications of the treatment of hadronic interactions, in the framework of the QGSJET-III model, in particular the model calibration to accelerator data, the amount of the “glue” in the pion, and the energy dependence of the pion exchange process. None of the considered modifications of the model allowed us to enhance the EAS muon content by more than 10%. On the other hand, for the maximal muon production depth, some of the studied modifications of particle production give rise up to $\sim 10$ g/cm${}^2$ larger $X_{max}^{\mu }$ values, which increases the difference with Auger observations.