Difference between revisions of "Particle ID"

Revision as of 13:05, 13 February 2015

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.
The timing χ² is defined as:
- Δt = t0() - time()
- χ² = (Δt/σ_Δt)

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 ** If neither is available, it's value is <span style="color:red">NaN</span> (and the detector system is <span style="color:red">SYS_NULL</span>).
 * <span style="color:#0000FF">DChargedTrackHypothesis</span>::<span style="color:#008000">measuredBeta</span>() is <span style="color:#008000">pathLength</span>()/(<span style="color:red">c</span>*(<span style="color:#008000">t1</span>() - <span style="color:#008000">t0</span>())).  Thus it is <span style="color:red">NaN</span> if there aren't enough detector hits on the track.
+* <span style="color:#0000FF">DChargedTrackHypothesis</span>::<span style="color:#008000">time</span>() is the hit time from the ST/BCAL/TOF/FCAL system propagated to <span style="color:#008000">position</span>().
+** 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.
+* The timing &chi;<sup>2</sup> is defined as:
+** &Delta;t = <span style="color:#008000">t0</span>() - <span style="color:#008000">time</span>()
+** &chi;<sup>2</sup> = (&Delta;t/&sigma;<sub>&Delta;t</sub>)
 == Neutral Showers ==