Alignment of the ATLAS Inner Detector Tracking System

In order to achieve the scientific goals, the alignment of the ATLAS Inner Detector tracking system requires the determination of its almost 36000 degrees of freedom (DoF) with high accuracy. Thus the demanded precision for the alignment of the silicon sensors is below 10 micrometers. The implementation of the track based alignment within the ATLAS software framework unifies different alignment approaches and allows the alignment of all tracking subsystems together. Primary vertex and beam spot constraints have also been implemented. As alignment algorithms are based on minimization of the track‐hit residuals, one needs to solve a linear system with large number of DoF. The solving involves the inversion or diagonalization of a large matrix that may be dense. The alignment jobs are executed at the CERN Analysis Facility, and also are moving to Grid. The event processing is run in parallel in many jobs. The output matrices from all jobs are added before solving. We will present the results of the alignment of the ATLAS Inner Detector using real data recorded during the LHC start up run in 2009 plus the recent 7 TeV data collected during 2010 run.