The ATLAS TRT performance in proton-proton and ion-ion collisions at the LHC

The Transition Radiation Tracker (TRT) is the outermost of the three sub-systems of the ATLAS Inner Detector at the Large Hadron Collider at CERN. It consists of close to 300000 thin-wall drift tubes (straws) providing on average 30 two-dimensional space points with 0.12-0.15 mm resolution for charged particle tracks with |η| < 2 and pT > 0.5 GeV. Along with continuous tracking, it provides particle identification capability through the detection of transition radiation X-ray photons generated by high-velocity particles in the many-polymer fibres or films that fill the spaces between the straws. This report gives the review of the TRT detector commissioning using cosmic muons studies and first operational experience in the proton-proton and ion-ion collisions at the LHC. The emphasis will be given to the TRT performance on the reconstruction and analysis of particle collisions. The first studies of the TRT detector response to the extremely high track density conditions during the November 2010 heavy-ion LHC running period will be presented. These studies give interesting insight to the expected performance of the TRT in future high-luminosity proton collider super-LHC.