Muon bundles from cosmic rays with ALICE

TL;DR

This paper analyzes atmospheric muon multiplicity detected by ALICE, comparing results with simulations, and finds high-multiplicity events suggest a heavy primary cosmic ray composition above 10^16 eV.

Contribution

It provides the first detailed analysis of high-multiplicity atmospheric muon events with ALICE and compares them with modern interaction models.

Findings

High-multiplicity muon events are consistent with heavy primary cosmic rays.

The frequency of these events matches models assuming heavy composition.

Results support a heavy mass composition of cosmic rays above 10^16 eV.

Abstract

ALICE, a general purpose experiment designed to investigate nucleus-nucleus collisions at the CERN Large Hadron Collider (LHC), has also been used to detect atmospheric muons produced by cosmic-ray interactions in the atmosphere. In this contribution the analysis of the multiplicity distribution of the atmospheric muons detected by ALICE between 2010 and 2013 is presented, along with a comparison with Monte Carlo simulations. Special emphasis is given to the study of high-multiplicity events, i.e. those containing more than 100 reconstructed muons. Such high-multiplicity events demand primary cosmic rays with energy above $10^{16}$ eV. The frequency of these events can be successfully described by assuming a heavy mass composition of primary cosmic rays in this energy range, using the most recent interaction models to describe the development of the air shower resulting from the primary interaction.