Cosmic Ray, Beam-Halo and Beam-Gas Rate Studies for ATLAS Commissioning

Prior to LHC beam-beam collisions, the first exposure of ATLAS to high-energy particles from cosmic rays, and also beam-halo and beam-gas events during single beam running, can be used for detector commissioning. The barrel calorimeter system should be able to take cosmic events already in 2005, and increasingly more sub-detectors will be installed and commissioned over the following two years. In late 2006 and early 2007, significant samples of cosmic ray events can be collected with the full ATLAS detector in place. In spring 2007, three months of LHC single-beam running are planned, which can be used to accumulate both beam-halo and beam-gas events for detector studies. Efficient use of these commissioning periods and data samples will prepare ATLAS for the first beam-beam collisions, expected in mid-2007. In this note, we present the first full simulation studies of the expected fluxes from cosmic ray muons, beam-halo muons and beam-gas events for the ATLAS commissioning period.