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Ghost Tracks

Ghost Tracks. Definition of ghost track Ghost track rate in MC Causes of ghosts Reco (mini) level ghost identification Remediation (ideas). Ghost Tracks. Ghost = 2nd track reconstructed from the same physical (charged) particle Not looper Not (necessarily) removed by GTL cuts

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Ghost Tracks

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  1. Ghost Tracks David Nathan Brown Definition of ghost track Ghost track rate in MC Causes of ghosts Reco (mini) level ghost identification Remediation (ideas)

  2. Ghost Tracks • Ghost = 2nd track reconstructed from the same physical (charged) particle • Not looper • Not (necessarily) removed by GTL cuts • Some others removed in BAD633 cuts • Provides no insight into the cause David Nathan Brown 2 Tracking meeting Jan. 19, 2005

  3. MC Studies • 18.2.0 Moose + BetaMini • Cond18boot from July 12 • Identify duplicate tracks using MC truth • I find 4.5% of ‘Default’ TrkRecoTrk are duplicates • Separate loopers from ghosts with • Charge •  • Overlap between hit layers • Compute fraction = (# of layers in common)/(total # of layers hit) • Scan some ghost track events • http://costard.lbl.gov/~brownd/tracking/ghosts/ David Nathan Brown 3 Tracking meeting Jan. 19, 2005

  4. David Nathan Brown 4 Tracking meeting Jan. 19, 2005

  5. Ghost finding in TrkFixup • Same charge • DOCA < 3 cm • Transverse radius at POCA > 10 cm •  at POCA < /4 • Hit layer overlap fraction < 0.15 • Only 1 track with >1 Svt hits • Separate ghost cause based on transverse radius • 80% of ghosts are Dch pat-rec problems (>30cm) • 20% are due to material scatters or E-loss (<30cm) David Nathan Brown 5 Tracking meeting Jan. 19, 2005

  6. David Nathan Brown 6 Tracking meeting Jan. 19, 2005

  7. Ghost Selection Results • >70% efficient on MC true ghosts • Inefficiency from dch pat-rec problems with • Very poor POCA • Spurious Dch or Svt hits picked up • Selected sample composition (MC truth) • 80% ghosts • 7% ‘inelastic’ hadronic scattering • 10% decay-in-flight • 90% K, 10%  • 3% random combinations (fakes) • 1 Svt-only plus 1 dch-only, many ‘junk’ tracks • No lost particle decays David Nathan Brown 7 Tracking meeting Jan. 19, 2005

  8. Ghost Repair (ideas) • Merge both tracks into a new single track • If present, use svt-track as trajectory seed • Re-enable disabled hots • Add a KalScatterSite for hard scatters • Adds 10-times the normal multiple scattering allowance • Add more (?) dE/dx uncertainty • Filter hits as necessary • Disable hits with  > 5 • Add a KalDecaySite for decays • Allows angles and momentum to change • If merged track refit fails • throw away ‘outer’ track • Keep ‘inner’ track for physics David Nathan Brown 8 Tracking meeting Jan. 19, 2005

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