BCAL reconstruction 10/19/11

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  • 1234 segmentation now an option in reconstruction code
  • New algorithm comparable to or better than KLOE algorithm in most tests I tried
    • Single photon events: (much) better timing resolution, better angular resolution, same energy resolution, but more extraneous clusters
    • Single pi0 events: ~5% more pi0's reconstructed
    • b1pi events: slightly more pi0's reconstructed
  • Will be checked in soon
  • Issues
    • pi0 reconstruction:
    • better errors
    • FCAL issues?


  • More flexible DBCALGeometry allows 1234 summing (checked-in)
  • Change weighting when averaging quantities to form cluster
  • Improve error estimation
  • Tune parameters
  • Fix various bugs
  • Change in KLOE algorithm to min energy threshold of cluster to make the two algorithms match

Single photon event sample

45000 events, energy uniformly distributed from .05-2.05 GeV, angles from 10.8-118. Exclude all events with tracking hits, since we can't expect to reconstruct a photon in this case. All results with 1234 summing.


Both algorithm have ~99.5% efficiency.

Energy resolution

Timing resolution

Angular resolution

Number of showers reconstructed

Single pi0 event sample

~64000 pi0's isolated from a bggen sample using extract_ptype_hddm plugin.

Again exclude any events with tracking hits.

Hard to get an exact count of how many pi0's are reconstructed/reconstructable, so I tried two different methods.

Method 1

Use DTwoGammaFit to fit two photons to pi0 mass. The problem with this is that it relies on having correct errors, which we don't quite have yet.

Just count the number of events where there is a pi0 fit with confidence level > 10%.

  • GlueX algorithm: 37163 good pi0 fits : 72% efficiency (excluding events with tracking hits)
  • KLOE algorithm: 34322 good pi0 fits : 66% efficiency

Energy and angular resolutions are roughly the same

Method 2

Look at the two most energetic photons in an event. If the combined four-momentum falls "close" to the thrown pi0 four-momentum, count this a "good" reconstructed pi0.

  • GlueX: 38342 good pi0's=74% efficiency
  • KLOE: 36083 good pi0's=70% efficiency

b1pi event sample

10000 b1pi events from genr8.

Can count the number of reconstructed BCAL photons "close" to thrown photons.

  • GlueX: 8266 "good" reconsructed BCAL photons/120
  • KLOE:

Vertex spread.

334 Segmentation


  • Errors/pi0 kinfit funniness
  • Cluster overlap function tweaks -> better energy resolution
  • Theta res distributions off-center
  • Very forward particles energy calibration, general energy calibration scheme
  • Extra showers at ~12 deg, low energy
  • What is cluster rho good for?