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ITS offline

ITS offline. Massimo Masera Torino. Open savannah bugs. Open savannah bugs. Material budget. Savannah bug 63965 Friederike Bock http://indico.cern.ch/conferenceDisplay.py?confId=87158 and http://indico.cern.ch/conferenceDisplay.py?confId=87662

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ITS offline

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  1. ITS offline Massimo Masera Torino

  2. Open savannah bugs ITS offline

  3. Open savannah bugs ITS offline

  4. Material budget • Savannah bug 63965 • Friederike Bock http://indico.cern.ch/conferenceDisplay.py?confId=87158 and • http://indico.cern.ch/conferenceDisplay.py?confId=87662 • Usage of 2 different V0 finders to check sysyematics • In ITS it seems that material budget is underestimated • Major differences around Z=0 ITS offline

  5. Material budget Beam pipe + SPD SDD1 SSD SDD2 ITS offline F. Bock March, 5-th

  6. Planning tool/1 ITS offline

  7. Planning tool/2 ITS offline

  8. ITS alignment & tracking(Slides from A. Dainese)

  9. Alignment • Alignment used for 2009 pp data: as of JINST paper • SPD alignment with cosmics 2008 (B=0), with Millepede • few modules on the sides “corrected” with pp data (see later) • SSD internal alignment from survey only (validated) • SPD-to-SSD alignment with Millepede • ITS-to-TPC alignment with cosmics + pp 2009 (Marian, Mikolaj) • In progress: • use pp data (B-on, B-off) to complete the alignment with Millepede2 (Ruben) • minimal alignment of the SPD side modules not covered by cosmics (~10% of SPD) • SDD calibration and alignment (see Francesco’s talk) • improvement of the full SPD, then SSD ladders • estimate of alignment / tracking precision with • extra clusters in module overlaps • cosmics B-on (Feb-2010 not yet properly reconstructed) ITS offline

  10. Alignment data filtering • AliTrackPoints extracted from ESDs+ESfriends (pass2) • Task PWG1/ITS/AliAlignmentDataFilterITS • extracts to a tree the ITS AliTrackPoints for selected tracks • also stored: • curvature and error from full track (ITS+TPC) • run number, B value • path of OCDB files for ITS alignment and calibration used in reco • needed by Millepede to get initial geometry conditions • Should become a task of the “2nd step calibration train” • All good runs processed (from run coord table) • 430,000 events B=0.5T • 100,000 events B=0 (430,000 tracks) • All points are in /alice/cern.ch/user/d/dainesea/ITSpoints/ • ~0.5 GB ITS offline

  11. SPD alignment with pp sides Ruben ITS offline

  12. Track rf impact parameter pt=1.0-1.5 GeV data MC PASS1 cosmics only cosmics + pp (f=0 and p) PASS4 data MC ITS offline

  13. Simulate with “data” geometry • Alignment results suggest that the real SPD geometry differs from the design (and AliRoot) one by a few 100 mm in some places (shape of carbon fiber sectors) Many large TGeo overlaps... Raffaele ITS offline

  14. Simulate with “data” geometry • Removing overlaps goes in parallel with understanding alignment  geometry could be changed once we are fully confident on alignment • there is a task (2583) related to changing the SPD geometry to make it "overlap free" after alignment: • a new ideal geometry with the sensitive volumes (ladders) in the same place where put by alignment has been already produced • behaviour w.r.t. alignment still under investigation ITS offline

  15. ITS tracking • In order to maximize tracking efficiency (TPC-to-ITS prolongation efficiency): assigned large “misalignment” errors to ITS clusters • 100 mm for SPD, 1 mm for SDD and SSD • Also limits the track precision, but this is not critical for the currect analyses • ITS+TPC tracks being used in all papers in preparation ITS offline

  16. TPC-ITS prolongation Data (104892) pass 4 MC LHC10a8 Track selection: nclsTPC>90, c2/cl<4, TPC ell. dca (2.4cm x 3.2cm), |h|<0.8 ITS offline 16

  17. TPC-ITS prolongation:Data Eff / MC Eff Data (104892) pass 4 MC LHC10a8 PYTHIA condition used in ongoing analyses • Possible reasons for the discrepancy: • ITS detector status (dead/noisy channels) not the same in MC and data • - misalignment and miscalibration • - larger fraction of secondaries in the data than in MC detailed checks ongoing in subdets. ITS offline

  18. Transverse impact parameter resolution from data • Methods: • top-bottom matching vs pt with cosmics (need 2010 cosmics) • fit central part of inclusive d0 distribution in pp • need to deconvolute vertex resolution • use statistical estimators in pp • intrisically disentangles track • and vertex resolution ITS offline

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