Problems with track finding in CDC

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Generated Lambda events with the particle gun. The following screen grabs from hdview2 illustrate a very common problem with these events: already used segments get associated erroneously with other already used segments to form bogus track candidates. Lambda1.png Lambda2.png Lambda3.png Lambda4.png

(March 5, 2012) Algorithm for dealing with bogus tracks

  • Compare bit map of hits between two CDC seeds
  • If 2 seeds share more than 90% of the same hits, keep the seed with the best χ^2/ndf from the circle fit
  • If 2 seeds share more than 50% of the same hits (but less than 90%) and the reduced χ^2 values of the circle fits from each seed differ by more than 1, keep the seed with the best χ^2/ndf from the circle fit; otherwise keep both

The same event as above using the new algorithm:

Lambda new algo.png

Generated 2500 Λ events, 0.1-2.1 GeV/c

  • Let GEANT decay the Λ
  • Compare results with (red) and without (black) the new algorithm

Lambda candidates.gif Lambda mass.gif

Generate 2500 K0(short) events, 0.1-2.1 GeV/c

  • Let GEANT decay the K0(short)
  • Compare results with (red) and without (black) the new algorithm

Kzero candidates.gif Kzero mass.gif