# PowerPoint Presentation by 4iO3wg50

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```									            STACO Status
Samira Hassani
DAPNIA/SPP/Saclay-France

Outline :

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

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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