Performance of the ATLAS Inner Tracker

ATLAS is a one of the four multipurpose experiments that records the products of the LHC proton-proton collisions at the LHC. In order to reconstruct the trajectories of charged particles, ATLAS is equipped, among others, with an inner charged particle tracking system built on two different technologies on silicon planar sensors (pixel and microstrips) plus drift-tube based detectors, all embedded in a 2 T solenoidal field. In order to achieve its scientific goals, ATLAS has quite demanding tracking performance requirements. Therefore, ATLAS is equipped, among others, with a charged particle tracking system built on two different technologies: silicon planar sensors and drift-tube based detectors constituting the ATLAS Inner Detector (ID). The ATLAS ID consists of about 6000 modules in its Silicon Tracker combined with several hundred drift tube based detector modules. The silicon modules use both technologies: pixel and microstrip. Pixel modules determine the position of passing particle tracks with an accuracy ~10 microns, whilst microstrip modules accuracy is about 20 microns. The drift tube based detector modules resolution is ~130 microns. However, the position of the devices after construction is only known much less accuracy than the intrinsic resolution. Therefore a track based alignment procedure has to be applied to determine the absolute position of the sensitive devices to a better precision. We will present the sta tus and performance of the ATLAS tracking system during the 2010 LHC run. The results obtained with proton-proton collisions as well as the recently acquired lead ion collisions will be shown.