Kinematic fitting charged particles 11/16/11

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Looking at an all charged particle final state to study the state of the tracking code: \gamma p -> pi+ pi+ pi- pi- p.

  • 50,000 events
  • svn revision 8540

Kinematic fit

All combinations of track hypotheses that produce the correct final state are kinematically fit. Constraint is overall conservation of 4-momentum.

  • 41% of events have sufficient particles (>=3 positive tracks, >=2 negative tracks)
  • Of these, 9% have kinematic fit confidence level>1% (4% of total events)


Kinematic fit is dependent on errors, PID. Try to simplify things...

Look at events with exactly 5 tracks (3 positive, 2 negative) and look at sum of reconstructed 3-momentum from all tracks.

28% of events have exactly 5 tracks

Pt vs pz.png

2400 events in region outlined in red.

Proton reconstruction

  • svn rev. 8574

Distribution of thrown protons in events:

Thrown protons.png

Look at sample of proton-only events with same momentum distribution.

Proton only.png

Protons with p<300 MeV/c are not detected, those with p>450 MeV/c almost always have sufficient hits.

Full event (5 particle final state) sample:

  • Examine only events with proton p>450 MeV (57% of total events)
  • 66% of events have good proton hit selection (all hits associated with proton hypothesis from proton track)
  • Of these events, only 54% have good fit (confidence level from tracking chi^2 > 1%)