The CERN's Large Hadron Collider (LHC) is the world largest particle accelerator. ATLAS is one of the two general purpose experiments equipped with a charge particle tracking system built on two technologies: silicon and drift tube based detectors, composing the ATLAS Inner Detector (ID). The required precision for the alignment of the most sensitive coordinates of the silicon sensors is just few microns. Therefore the alignment of the ATLAS ID requires complex algorithms with extensive CPU and memory usage. So far the proposed alignment algorithms are exercised on several applications. We will present the outline of the alignment approach and results from Cosmic Ray runs and large scale computing simulation of physics samples mimicking the ATLAS operation during real data taking. The full alignment chain is tested using that stream and alignment constants are produced and validated within 24 hours. Cosmic ray data serves to produce an early alignment of the real ATLAS Inner Detector even before the LHC start up. Beyond all tracking information, the assembly survey data base contains essential information in order to determine the relative position of one module with respect to its neighbors.
Jochen Schieck (Max-Planck-Institut für Physik)
Andrea Bocci (Unicersity of Duke) Anthony Morley (University of Melborne) Ben Cooper (Queen Mary University) Carlos Escobar (IFIC) Max Scherzer (University of Berkely) Muge Karagoz Uenel (University of Oxford) Oleg Brandt (University of Oxford) Pawel Bruckman de Rennstrom (University of Oxford) Regina Moles (IFIC) Salvador Marti i Garcia (IFIC) Tobias Golling (University of Berkely) Vicente Lacuesta (IFIC)