L3 Tracking Studies at Imperial

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L3 Tracking Studies at Imperial

• R. Beuselinck
• 26 March 2003

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Outline

• CFT tracker developments
• Tracker comparison analysis
• Method
• Problems
• Definitions
• Results
• Efficiency, purity
• timing

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CFT Tracker Developments

• Ongoing work to improve CFT tracker
• Timescale 2 weeks for new release
• Goals
• Improve axial tracking efficiency purity
• Speed up the code
• Comparison with current CFT code and Global
  Tracker (CFT only)

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ttbar current CFT code
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ttbar updated CFT
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current CFT code green tracks have large chisquare
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2nd event current code
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2nd event updated code
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Tracker Analysis Method

• Compare tracking tool output to MC or real data
  tracks by cluster matching.
• Define matches by shared clusters and track
  parameter comparison.
• Use standard L3TTracker interface.
• Can run as an additional package in tsim_l3.

Original code by Chris Barnes, modified by Tim
Scanlon
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Problems encountered

• Want to define matching by shared clusters
• Existing MC files dont keep assignment of
  clusters to MC tracks
• Existing trackers keep cluster assignment
  differently (not part of L3TTracker interface)
• Match by cluster proximity instead.
• Timing results lose overflow information

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Definitions cluster matching

• Clusters are assigned to MC tracks and L3 tracks
  by proximity
• Stereo clusters must be within 2cm in Z
• Axial clusters within 0.2/Rlayer in phi
• Original analysis code used clusters assigned by
  CFT tracker
• Results are almost identical to proximity
  assignment method.

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Definitions track matching

• Which MC track is best match to L3 track ?
• The one with the most shared clusters
• Symmetric definition for reverse match
• For real data offline reco tracks are treated as
  MC tracks for analysis of L3 trackers.

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MC Track categories

• Findable MC track
• Pt gt 1.0GeV/c, eta lt 1.6,
• dca lt 1.0cm, Z0 lt 1m
• At least 8 CFT clusters matched to track
• Missed MC track
• No assigned cluster matches any L3 track

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L3 track categories

• Good L3 track
• Matches at least 8 clusters to one MC track
• Track parameter difference chisquare lt400
• Found track
• Matches at least 1 cluster to an MC track but
  fails one of preceding cuts
• Fake track
• Anything else

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Relationship of track categories
MC
good
fake
missed
L3
found
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Definitions efficiency, purity

• Efficiency found / findable
• Good efficiency good / findable
• Purity good / (found fake)
• good / L3 tracks

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ttbar Global Tracker (CFT only)
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ttbar Original CFT code
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ttbar updated CFT code
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ttbar original CFT code
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ttbar updated CFT code
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ttbar Global Tracker (CFT only mode)
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QCD Original CFT code
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QCD Updated CFT code
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QCD Global Tracker (CFT only mode)
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Real Data Original CFT code
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Real Data Updated CFT code
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Real Data Global Tracker (CFT only mode)