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SSD status report

SSD status report . Enrico Fragiacomo on behalf of SSD Offline week, CERN 22/06/09. Outlook. Time response in simulation ( tasks 2586 and 2587 ) Bad channels in reconstruction ( Savannah ) Offline gain calibration. Time response in simulation (EF).

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SSD status report

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  1. SSD status report Enrico Fragiacomo on behalf of SSD Offline week, CERN 22/06/09

  2. Outlook • Time response in simulation (tasks 2586 and 2587) • Bad channels in reconstruction (Savannah) • Offline gain calibration

  3. Time response in simulation (EF) • Changes in AliITSsimulationSSD from rev. 32606 ... tof = mod->GetHit(i)->GetTOF(); if (tof<2.) de = de * fTimeResponse->Eval(-1.*tof+2.); else de = 0. … • fTimeResponse defined according to HAL25 time response: • The charge from a particle in the trigger is shaped and sampled after 2 microsec • A particle in the past (wrt trigger) is always seen at sampling time (tail) • A particle in the future is seen up to 2 microseconds sampling time

  4. Improvements in the CF (EF) • Changes in the CF (AliITSClusterFinderV2SSD) from rev. 32604 • Diagonal matrices (out-of-diagonal elements correctly treated) • 1D-cluster unfolding to kFALSE by default • Difference replaced by ratio in charge-matching filter • Bad-good crosses: • New cluster type introduced • Includes bad-side modules as sub case (savannah #47413) • BTW savannah #47413 waits for the tracking part to be done soon (Andrea D.) • BTW bad modules or bad areas already treated at tracking level (Andrea D. and Marco vL.) • Requires minors changes in AliCluster.h, AliITSRecPoint.cxx and in AliITSRecoParam.cxx

  5. SSD calibration task (1/2) (Marek C.) • Aims at calibrating the gains: • Presently foreseen at module level (small fluctuations at strip level) • An additional field (charge ratio) added to the AliTrackPoint class: • Needed to perform both the absolute and the per-side gain calibration in one go • First version of the wagon ready (sent to Cvetan; Marek is waiting for inputs for further developments)

  6. SSD calibration task (2/2) • The task reads the charge and the P-to-N charge ratio (CR) from the AliTrackPoint • selects MIPs and corrects for the inclination • produces two TH2F with the module number on one axis and the charge (or CR) on the other • post-processing procedure produces gain parameters for the OCDB • human intervention needed to give the green light for OCDB update

  7. Conclusions • Time response in simulation (closed task) • Bad channels in reconstruction (in Savannah) • Offline gain calibration (in progress...)

  8. Extras

  9. Covariance matrix 800 mm • Old situation in the CF • Did not take into account angles! • No out-of-diagonal element in the covariance matrix • 20 mm underestimates error 20 mm S’=ASAT with A the transformation from PN to yz system Z N Y P sP,N=1/√2=0.083 in unit of pitch if 1Dcluster has one strip sP,N=20mm/95mm=0.044 in unit of pitch if 1Dcluster is wider

  10. Covariance matrix

  11. Covariance matrix (special case) • How was previously implemented • WRONG!! • No out-of-diagonal element in the covariance matrix • 20 mm underestimates error e.g. Bad N 4/√2 cm 20 mm S’=RSRT with R the transformation (rotation) from P”N” to yz system Z “N” Y sP=1/√2=0.083 in unit of pitch if 1Dcluster has one strip sP=20mm otherwise sN= 4/√2 cm=1.15 cm P

  12. Covariance matrix (special case)

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