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									            STACO Status
       Samira Hassani
   DAPNIA/SPP/Saclay-France

Outline :

 Introduction
 Principle of STACO
 STACO in Athena
 Prospects
             Track Combination

  Combination of measurements made in
  the Muon system with the one from
  the inner detector:
         Improve the momentum resolution in the
         momentum range 6 GeV <pT < 100 GeV
         Allow the rejection of muons from
         secondary interaction and the ones from /
         decays in flight

ATLAS Overview Week 6/10/2004       Samira Hassani   2
Track Combination Procedures
• To combine tracks in the inner detector and the Muon
  system, two strategies can be used:

• STACO : STAtistical COmbination of two
  measurements made in the Muon System with the one
  from the Inner Detector using the reconstructed
  tracks and their covariance matrices

• MUID : global fitting of the muon track using the hits
  from the two subdtectors which were found and used
  separately by the standalone reconstructions



 ATLAS Overview Week 6/10/2004      Samira Hassani   3
                  Principle of STACO
• For two tracks on some reference location defined by their :
         Parameters vectors : P1 and P2
         Covariance matrices : C1 and C2
• P: parameters vectors of combined track is the solution of the equation:
                         (C11  C21 )  P  C11  P1  C21  P2
    C : covariance matrix of combined track is given by
                                         C  (C11  C21 ) 1
•   The corresponding    2
        2  ( P  P )T  C11  ( P  P )  ( P  P2 )T  C2 1  ( P  P2 )
                    1                   1
                                                            


•  Track combination is tried only for pairs of tracks that show a
  reasonable matching in the (,) plane
• Track combination is accepted only if the global 2 is below a maximal
  value
• If different combinations are possible, the pair given the best 2 is
  retainedOverview Week 6/10/2004
     ATLAS                                       Samira Hassani     4
                              STACO Basics
•   The track reconstruction in the Inner Detector is performed by
                      xKalman++ or iPatRec packages

• The track reconstruction in the Muon System is performed by
                     Muonboy or Moore packages

•   The correction for energy loss in the calorimeters are done in
    Muonboy and MuidStandalone

•   The effects of multiple scattering and energy losses fluctuations have
    been taken into account in the covariance matrix propagation given by
    Muonboy and MuidStandalone


      ATLAS Overview Week 6/10/2004              Samira Hassani      5
                STACO is in ATHENA 8.8.0
   offline/Reconstruction/MuonIdentification/STACO

                         Tracker digits                      Inner Detector
                          Tracks                           xKalman++/iPatRec


                          MS digits
   StoreGate                Tracks                          Muon Spectrometer
 Transient Event                                          Muonboy/MuidStandalone
   Data Store

                                      ID Track
                                      MS Track
                                                                STACO
                           Combined Tracks

Output: Track Parameters, Covariance Matrix,   2   are directly available in CBNT
   ATLAS Overview Week 6/10/2004                     Samira Hassani        6
                         STACO in ATHENA
STACO and New EDM
 • Inputs can be package specific containers or the common EDM objects
 (TrackParticle)
 •Outputs available in 3 formats: STACO specific object, TrkTrack or
 TrackParticle containers in 8.8.0

TrackParticle Conversion Validation

      specific containers
                                        TrackParticle
                       Entries=1090      Entries=1090
                       Mean=0.00097      Mean=0.00090




    ATLAS Overview Week 6/10/2004            Samira Hassani     7
STACO Performance :                Distributions of 1/pT pull

    xKalman / Muonboy                  iPatRec/ Muonboy



   100 GeV

                   σ =1.04 ±0.04                        σ =1.05 ±0.04




             Consistency of the covariance matrices
ATLAS Overview Week 6/10/2004          Samira Hassani          8
STACO Performance :                 Distributions of 1/pT pull

xKalman / MuidStandalone            iPatRec/ MuidStandalone


   100 GeV


                    σ =1.06 ±0.04                        σ =1.05 ±0.04




              Consistency of the covariance matrices
 ATLAS Overview Week 6/10/2004          Samira Hassani          9
Prospect to Improve Combined Efficiency
               at High PT
                                  Slow decrease of combined efficiency
                                   with increasing PT

                                   It has been shown that a fraction of
                                  tracks lost in combination, have a good
                                  momentum resolution in the MS

                                         but are slightly phi shifted in
                                         the transverse plane because
                                         electromagnetic showers have
                                         spoiled the hit pattern

                        pT(GeV)         Use STACO algorithm as trigger
                                  to redo track reconstruction in the Muon
                                  Spectrometer with a constrain from
                                  Inner Detector
 ATLAS Overview Week 6/10/2004                   Samira Hassani      10
                          Conclusion
• STACO procedure works because the ID and
  Muon system measurements are independent

• STACO is working in Athena 8.8.0

• Next, STACO as an algorithm to detect and
  redo spurious track reconstruction in the
  Muon spectrometer


  ATLAS Overview Week 6/10/2004    Samira Hassani   11

								
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