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Track reconstruction and hyperon Track reconstruction and hyperon simulationssimulations
Evgeny Kryshen (PNPI, SPbSPU)
28 Feb 2005 CBM Collaboration meeting 2
OutlineOutline
• Analysis strategy and simulation of STS detector inefficiencies
• Impact of STS detector inefficiencies on tracking
• Tracking performance for 8 station setup
• Impact of STS detector inefficiencies for 8 station setup
• Tracking performance for 9 station setup
• Replacing hybrid stations with strips
• Studies of the half-length strip configuration
• Conclusions and outlook
28 Feb 2005 CBM Collaboration meeting 3
Analysis strategyAnalysis strategy
• No pile-up in MAPS stations is assumed• “Realistic” station thickness and strip pitch• 1 level of the the CA track finder (primary search)• Statistics: 100 central 25 GeV UrQMD events• Active shielding field map• Performance criteria:
Tracking performance - all tracksTracking performance - primariesTracking performance – lambda (2 level – all search)Momentum resolutionTime consumption
28 Feb 2005 CBM Collaboration meeting 4
““Realistic” geometry vs CVSRealistic” geometry vs CVS
“Realistic” geometry (sts-2maps-1pix-4strips.geo + sts_digi_50.par):
Type: Z Position: Thickness: Resolution:
Maps 5,10 cm 150 μm sigma = 5 μm
Hybrid 20 cm 700 μm pixel size = 50 μm
Strips 40,60,80,100 cm 400 μm pitch = 50 μm
“Realistic” geometry (sts-2maps-1pix-4strips.geo + sts_digi_50.par):
Type: Z Position: Thickness: Resolution:
Maps 5,10 cm 150 μm sigma = 5 μm
Hybrid 20 cm 700 μm pixel size = 50 μm
Strips 40,60,80,100 cm 400 μm pitch = 50 μm
CVS geometry (sts-3maps-4strips.geo + sts_digi.par):
Type: Z Position: Thickness: Resolution:
Maps 5,10 cm 100 μm sigma = 5 μm
Hybrid 20 cm 100 μm pixel size = 50 μm
Strips 40,60,80,100 cm 200 μm pitch = 25 μm
CVS geometry (sts-3maps-4strips.geo + sts_digi.par):
Type: Z Position: Thickness: Resolution:
Maps 5,10 cm 100 μm sigma = 5 μm
Hybrid 20 cm 100 μm pixel size = 50 μm
Strips 40,60,80,100 cm 200 μm pitch = 25 μm
28 Feb 2005 CBM Collaboration meeting 5
Efficiency simulationEfficiency simulation
• Hit efficiency is already implemented in MAPS hit producer (flag = -1 in the case of lost hits)
• Hybrid pixel hit efficiency was added into Hybrid pixel hit producer
• Strip efficiency is added for each side of the strip station
• In the present analysis equal efficiency rate is set for all detector types
28 Feb 2005 CBM Collaboration meeting 6
Tracking vs STS efficiencyTracking vs STS efficiency
CA track finder performance is almost the same:
AllSet: 0.89 -> 0.87,RefSet: 0.97-> 0.94
28 Feb 2005 CBM Collaboration meeting 7
8 station geometry8 station geometry
Type: Z Position: Thickness:
Maps 5,10 cm 150 μm
Hybrid 20,30 cm 700 μm
Strips 40,60,80,100 cm 400
μm
Type: Z Position: Thickness:
Maps 5,10 cm 150 μm
Hybrid 20,30 cm 700 μm
Strips 40,60,80,100 cm 400
μm
Geometry: sts-2maps-2pix-4strips.geo Strips: sts_digi_50_5-8.par
Geometry: sts-2maps-2pix-4strips.geo Strips: sts_digi_50_5-8.par
28 Feb 2005 CBM Collaboration meeting 8
Track reconstruction with 8 STS stationsTrack reconstruction with 8 STS stations
Parameter 7 stations 8 stationsRefPrim /event 363 397AllSet /event 503 573Ghosts/event 26.2 13.2Clones/event 1.4 6.7RECO Lambda / event 2.5 4.0CPU sec. / event 141 134Momentum resolution 1.00% 1.18%
At 99% STS hit efficiency
Advantages of the 8 station:• significant increase (12%) in the number of reconstructed tracks• less calculation time• 60% increase in the number of reconstructed Lambda decays• More stable to STS hit inefficiencies• 2 times lower ghost rate
Advantages of the 8 station:• significant increase (12%) in the number of reconstructed tracks• less calculation time• 60% increase in the number of reconstructed Lambda decays• More stable to STS hit inefficiencies• 2 times lower ghost rate
Statistics: 100 events
Disadvantages of the 8 station:• increase in clones rate (1.4 6.7)• decrease in momentum resolution (1.00% 1.18%)
Disadvantages of the 8 station:• increase in clones rate (1.4 6.7)• decrease in momentum resolution (1.00% 1.18%)
28 Feb 2005 CBM Collaboration meeting 9
Tracking vs STS efficiency (7 or 8 stations)Tracking vs STS efficiency (7 or 8 stations)
8 stations – better resistance to the STS hit inefficiency
28 Feb 2005 CBM Collaboration meeting 10
Momentum resolution vs STS hit efficiencyMomentum resolution vs STS hit efficiency
Worse momentum resolution:
8 stations – 1.14 %7 stations – 0.97 %
Possible solution: use strip stations
28 Feb 2005 CBM Collaboration meeting 11
Ghosts and clones (8 stations)Ghosts and clones (8 stations)
Advantages of the 8 station:• Lower ghost rate• Better resistance to the STS
inefficiency
Advantages of the 8 station:• Lower ghost rate• Better resistance to the STS
inefficiency
28 Feb 2005 CBM Collaboration meeting 12
9 STS stations9 STS stations
Problem: what could we gain from the additional 9th station?
Type: Z Position: Thickness:
Maps 5,10 cm 150 μm
Hybrid 20,30 cm 700 μm
Strips 40,55,70,85,100 cm 400
μm
Type: Z Position: Thickness:
Maps 5,10 cm 150 μm
Hybrid 20,30 cm 700 μm
Strips 40,55,70,85,100 cm 400
μm
Geometry: sts-2maps-2pix-5strips.geo Strips: sts_digi_50_5-9.par
Geometry: sts-2maps-2pix-5strips.geo Strips: sts_digi_50_5-9.par
Additional strip station inserted. 5 equidistant strip stations are parameterized with the usual sector geometry applying simple sector scaling
28 Feb 2005 CBM Collaboration meeting 13
Track reconstruction with 9 STS stationsTrack reconstruction with 9 STS stations
Parameter 7 stations 8 stations 9 stationsRefPrim /event 363 397 401AllSet /event 503 573 583Ghosts/event 26.2 13.2 15.6Clones/event 1.4 6.7 11.4RECO Lambda / event 2.5 4.0 5.7CPU sec. / event 141 134 82Momentum resolution 1.00% 1.18% 1.32%
At 99% STS hit efficiency
Advantages of the 9 station:• slight increase (2%) in the number of reconstructed tracks• 40% increase in calculation time performance• 40% increase in the number of reconstructed Lambda decays• More stable to STS hit inefficiencies
Advantages of the 9 station:• slight increase (2%) in the number of reconstructed tracks• 40% increase in calculation time performance• 40% increase in the number of reconstructed Lambda decays• More stable to STS hit inefficiencies
Statistics: 100 events
Disadvantages of the 9 station:• increase in ghost rate (13.2 15.6)• increase in clones rate (6.7 11.4)• decrease in momentum resolution (1.18% 1.32%)
Disadvantages of the 9 station:• increase in ghost rate (13.2 15.6)• increase in clones rate (6.7 11.4)• decrease in momentum resolution (1.18% 1.32%)
28 Feb 2005 CBM Collaboration meeting 14
Strips vs hybrids (7 station setup)Strips vs hybrids (7 station setup)
Do we need the third technology (hybrid pixels)? What we get when replacing hybrids with strips?
Parameter 3 station - hybrid
3 station – strips
RefPrim /event 363 351
AllSet /event 503 472
Ghosts/event 26.2 54.0
Clones/event 1.4 0.8
RECO Lambda / event 2.5 2.4
CPU sec. / event 141 176
Momentum resolution 1.00% 0.96%
• 6% decrease in the number of rec. tracks• Small gain in momentum resolution• 2 times higher ghost rate
• 6% decrease in the number of rec. tracks• Small gain in momentum resolution• 2 times higher ghost rate
• 3rd hybrid station (700 μm) replaced with strip station (400 μm).
• Simple scaling of strip sector geometry (minimum strip length – 1 cm)
28 Feb 2005 CBM Collaboration meeting 15
Strips vs hybrids (8 station setup)Strips vs hybrids (8 station setup)
Can we achieve better momentum resolution by replacing hybrids (700 μm) with strips (400μm)?
Parameter 3,4 station - hybrid
3,4 station –
strips
RefPrim /event 397 375
AllSet /event 573 518
Ghosts/event 13.2 52.7
Clones/event 6.7 7.6
RECO Lambda / event 4.0 ?
CPU sec. / event 134 272
Momentum resolution 1.18% 1.10%
• 10% decrease in the number of rec. tracks• 0.08% gain in momentum resolution• 4 times higher ghost rate
• 10% decrease in the number of rec. tracks• 0.08% gain in momentum resolution• 4 times higher ghost rate
• 3 and 4 hybrid stations (700 μm) replaced with strip stations (400 μm).
• Simple scaling of strip sector geometry (minimum strip length – 1 cm)
28 Feb 2005 CBM Collaboration meeting 16
Strips vs hybrids (9 station setup)Strips vs hybrids (9 station setup)
Can we achieve better momentum resolution by replacing hybrids (700 μm) with strips (400μm)?
Parameter 3,4 station - hybrid
3,4 station –
strips
RefPrim /event 401 381
AllSet /event 583 537
Ghosts/event 15.6 53.8
Clones/event 11.4 13.2
RECO Lambda / event 5.7 4.7
CPU sec. / event 82 211
Momentum resolution 1.32% 1.24%
• 8% decrease in the number of rec. tracks• 0.08% gain in momentum resolution• 3.5 times higher ghost rate
• 8% decrease in the number of rec. tracks• 0.08% gain in momentum resolution• 3.5 times higher ghost rate
• 3 and 4 hybrid stations (700 μm) replaced with strip stations (400 μm).
• Simple scaling of strip sector geometry (minimum strip length – 1 cm)
28 Feb 2005 CBM Collaboration meeting 17
Half-length strip parametrizationHalf-length strip parametrization
Parameter Full-length, 7 stations
Half-length, 7 stations
RefPrim /event 377 376
AllSet /event 523 532
Ghosts/event 20.3 10.5
RECO Lambda / event
35 43
CPU sec. / event 141 35
Momentum resolution
0.974% 0.977%
28 Feb 2005 CBM Collaboration meeting 18
Conclusions and outlookConclusions and outlook
• 7 station setup is quite sensitive to the STS inefficiencies
• 8 station setup allows to improve track reconstruction performance significantly,
the only drawback – lower momentum resolution
• 9 station setup – slight improvement in track reconstruction performance, further
increase of reconstructed lambda
• Hybrid stations are desirable in respect to the track finding
• CPU consumption is very sensitive to the number and type of STS stations
• Reduction of strip length does not provide a significant gain in track reconstruction
• New “realistic” sector geometry (J. Heuser) to be tested