Detección de muones atmosféricos en el experimento ALICE-LHC

The calibration, alignment and commissioning of most of the ALICE (A Large Ion Collider Experiment at the CERN LHC) detectors have required a large amount of cosmic events during 2010, 2011, 2012 and 2013. Two main triggers were implemented to collect the atmospheric muons crossing the experiment. The first trigger, called “ACORDE trigger”, is generated by 60 scintillators located on the top three sides of the L3 magnet surrounding the central detectors, and selects single muons and bundles of atmospheric muons. The second trigger, called “TOF trigger”, is obtained by requiring a simultaneous signal on some pads of the Time of Flight (TOF) detector. The analysis of multi-muon events triggered by ACORDE and TOF and reconstructed using the ALICE Time Projection Chamber (TPC) is presented. A special emphasis in the study of muon bundles, with a particular attention on high muon density events is discussed. In particular the muon multiplicity distribution, that gives information on the primary cosmic ray composition in the energy range around the knee, has shown some unexpected events of very high multiplicity.