FCAL Reconstruction in b1pi events 03/06/2012
From GlueXWiki
Thrown photons
Reconstructed photons
(after vetoing cluster matched to charged tracks)
Questions
- Why are so many "photons" reconstructed? How can we reduce this?
- What is the actual reconstruction efficiency?
- How many photons reach the FCAL without converting?
- Efficiency for non-converting photons?
- Can we recover converted photons?
- Energy resolution, etc.
1 GeV photon events
Mihajlo in GlueX-doc-823 (2007) says for 1 GeV photons:
- 99.6% efficiency for photons that reach FCAL
- 37% photon conversion before FCAL
- Taking into account single clusters from photons that converted close to the FCAL face, the overall photon reconstruction efficiency was estimated to be 77%
- 4% energy resolution at 1 GeV
Has anything changed since 2007? How does b1pi sample differ from single photon sample?
Efficiency
Energy distribution of thrown photons:
- Black=all thrown photons
- Red=photons which reach the FCAL without converting (determined using DFCALTruthShower object)
- Blue=photons which reach the FCAL without converting AND are reconstructed successfully (fabs(theta_thrown - theta_recon) < .004 && fabs(phi_thrown - phi_recon) < .08)
Red/Black
Roughly 20% of photons convert before reaching FCAL. Relatively constant across wide range of energy. There is an angular dependence, not shown here. Big improvement since 2007 (geometry change?)
Blue/Red
98% of uncoverted
