Commissioning of the Charged Lepton Identification with Cosmic Rays in ATLAS

The ATLAS detector is designed for the study of highly energetic proton proton collisions at the LHC and offers excellent charged lepton identification. Millions of cosmic rays recorded by the ATLAS detector in fall 2008 and summer 2009 were used to commission the charged lepton identification algorithms. Fake tau candidates allowed the verification of the distribution of tau identification variables predicted by Monte-Carlo simulations. Electrons produced by highly energy muons during the passage through the detector material were successfully identified by expoiting the transition radiation capability of the inner detector. The huge statistics of muon tracks allowed the alignment of the inner detector and muon spectrometer guaranteeing excellent muon momentum resolution and efficiency at the start of the LHC.