Multimuon Events from Cosmic Rays with the ALICE Detector

Abstract

ALICE experiment at the CERN's Large Hadron Collider, carried out a cosmic data-taking campaign in the period 2015-2018 (LHC Run 2), for a total of 62.5 days of real observation time. In this contribution, the analysis of these data is limited to multimuon events, i.e. events with more than four detected muons. In particular, the muon multiplicity distribution (MMD) is studied in the low-intermediate multiplicity range ($4 < N_μ < 50$), while for multiplicities $N_μ > 100$, dominated by large statistical fluctuations of the data, the rate of the high muon multiplicity events (HMM) is measured. The results are compared with Monte Carlo simulations using three of the main hadronic interaction models describing the air shower development in the atmosphere: QGSJET-II-04, EPOS-LHC, and SIBYLL 2.3d, and assuming two extreme compositions of primary cosmic rays, pure proton and pure iron, representing respectively the lightest and the heaviest composition. Although the models have difficulty precisely describing the trend of primary p and Fe as a function of cosmic ray primary energy, QGSJET-II-04 is the only model that reproduces reasonably well the MMD and the rate of HMM events assuming a heavy composition for the entire energy range studied.