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ID Alignment: CSC

ID Alignment: CSC. The ATLAS CSC (Computing System Commissioning) served to validate the ATLAS ID Alignment algorithms with large MC samples Our group participates in the Globalχ 2 silicon alignment based on the tracks χ 2 minimization

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ID Alignment: CSC

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  1. ID Alignment: CSC • The ATLAS CSC (Computing System Commissioning) served to validate the ATLAS ID Alignment algorithms with large MC samples • Our group participates in the Globalχ2 silicon alignment based on the tracks χ2 minimization • Needs to invert (diagonalize) a NAlixNAli matrix (up to 35k x 35k)

  2. ID Alignment: CSC • During the CSC the ID alignment strategy was settle level by level • From big structures (few DoFs) • Barrel layers and end caps disks (hundreds of DoFs) • To modules (35K DoFs)

  3. ID Alignment: CSC • Results of the Globalχ2 method during the CSC were used in the ATLAS detector paper • The ATLAS Collaboration, G. Aad et al., • The ATLAS Experiment at the CERN Large Hadron Collider, • JINST 3 (2008) S08003

  4. ID Alignment operation scheme

  5. ID Alignment FDR • The 2008 ATLAS Full Dress Rehearsals main purpose was an evaluation of different data streaming techniques for physics analysis and calibration • The calibration and alignment was run like in real data taking with a 24 hours loop • We participated actively in all FDR exercises • Running the alignment jobs • Producing alignment constants • Reporting at the daily operations meetings • Validating the alignment constants • Our alignment constants were used for the official production

  6. ID Alignment FDR • During the 2008 ATLAS FDRs the alignment scheme was implemented, tested and validated. The Ringberg ID alignment scheme

  7. ID Alignment with real cosmic data 2008 • During the fall of 2008, ATLAS collected several millions of real cosmic ray tracks. • They served to commission the real detector • Align the real Inner Detector with real data

  8. ID Alignment with real cosmic data 2008 • Our first set of alignment constants with the Globalχ2 was validated 18th /September/2008 and it was ready to reconstruct the first LHC collisions expected the following day • The experience with the real data helped to identify new alignment levels (not anticipated in the simulation) to account for collective movements of modules during the assembly • Pixel half shells • Pixel and SCT ladders

  9. ID Alignment with real cosmic data 2008 • Our Globalχ2 set of constants are used for the • Official ATLAS cosmic data reprocessing • By the Cosmic analysis group • Validation performed with track splitting in upper and lower segment and check the matching

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