Speaker
Description
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. The large size and excellent tracking capability of the ALICE Time Projection Chamber are exploited to detect and reconstruct these muons. A program of cosmic-ray data taking was started in 2010 in periods when there is no beam circulating in the LHC. To date ALICE has acquired several million events with at least one muon. After a short summary of the previous LEP results, 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 1016 eV, and it will be shown that the frequency of these events can besuccessfully 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.