Particle ID

Charged Tracks

• DChargedTrackHypothesis::position() returns the position of the track at its position of closest approach to the beamline.
• DChargedTrackHypothesis::t1() is the measured hit time of the BCAL/TOF/FCAL hit/shower, if present, that is matched to the track (if hits in multiple systems, order of preference is BCAL/TOF/FCAL).
  • If it is not matched to a hit, it's value is NaN (and the detector system is SYS_NULL).
• DChargedTrackHypothesis::pathLength() returns the path length along the track from it's hit in the BCAL/TOF/FCAL to position().
• DChargedTrackHypothesis::t0() is either:
  • The selected RF bunch time, if present, propagated to position().
  • The measured start counter hit time, if present, propagated to position().
  • If neither is available, it's value is NaN (and the detector system is SYS_NULL).
• DChargedTrackHypothesis::measuredBeta() is pathLength()/(c*(t1() - t0())). Thus it is NaN if there aren't enough detector hits on the track.
• DChargedTrackHypothesis::time() is the hit time from the ST/BCAL/TOF/FCAL system propagated to position().
  • This propagation is performed step by step along the track, taking into account the energy loss of the particle at each step. Thus, it is not calculated with a constant beta.
• DChargedTrackHypothesis::dChiSq_Timing is defined as:
  • Δt = t0() - time()
  • χ² = (Δt/σ_Δt)²
  • With NDF = 1 (0 if not enough matching detectors).