Difference between revisions of "FCAL Reconstruction in b1pi events 03/06/2012"
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| + | svn rev. 8810. 50,000 b1pi events. No EM background. | ||
===Thrown photons=== | ===Thrown photons=== | ||
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===1 GeV photon events=== | ===1 GeV photon events=== | ||
Mihajlo in GlueX-doc-823 (2007) says for 1 GeV photons: | Mihajlo in GlueX-doc-823 (2007) says for 1 GeV photons: | ||
| − | |||
* 37% photon conversion before FCAL | * 37% photon conversion before FCAL | ||
| + | * 99.6% efficiency for photons that reach 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% | * 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 | * 4% energy resolution at 1 GeV | ||
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* Black=all thrown photons | * Black=all thrown photons | ||
* Red=photons which reach the FCAL without converting (determined using DFCALTruthShower object) | * 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) < . | + | * Blue=photons which reach the FCAL without converting AND are reconstructed successfully (fabs(theta_thrown - theta_recon) < .006 && fabs(phi_thrown - phi_recon) < .15) |
[[File:PhotonE_thrown_FCAL_all_truthshower_truthshower%2Brecon.png]] | [[File:PhotonE_thrown_FCAL_all_truthshower_truthshower%2Brecon.png]] | ||
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[[File:Photon_FCAL_recon_eff.png]] | [[File:Photon_FCAL_recon_eff.png]] | ||
| − | Above 1 GeV, | + | Above 1 GeV, 99.2% of uncoverted photons are reconstructed. This is less than the 99.6% reported for single photon sample, most likely this difference is due to photon showers overlapping with charged particle shower. |
Below ~600 MeV, efficiency drops. This is due to showers contained within a single cell, which means no cluster is created. | Below ~600 MeV, efficiency drops. This is due to showers contained within a single cell, which means no cluster is created. | ||
| − | Overall FCAL reconstruction efficiency considering only | + | Overall FCAL reconstruction efficiency considering only unconverted photons: 74%. Could be higher after trying to recover photons that convert. |
===Extra photon problem=== | ===Extra photon problem=== | ||
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* The match radius is hardcoded as 5 cm, but in the calib/PID/photon_track_matching this parameter is set to 15 cm. Change this back to 15 cm. | * The match radius is hardcoded as 5 cm, but in the calib/PID/photon_track_matching this parameter is set to 15 cm. Change this back to 15 cm. | ||
| − | + | Also use a timing cut (t_shower-t_flight) < 1.2 ns to cut out of out-of-time particles: | |
| + | |||
| + | [[File:PhotonTproj recon FCAL.png]] | ||
| + | |||
| + | More aggressive cluster matching reduces average number of "photons" per event from 2.5 to 1.5. Timing cut on top of this reduces average to 1.2. (actually 0.77 photons should hit the FCAL per event) | ||
| + | |||
| + | This also reduces efficiency (as defined above) from 74% to 70%. Timing cut has negligible effect on efficiency. | ||
Latest revision as of 13:00, 14 March 2012
svn rev. 8810. 50,000 b1pi events. No EM background.
Contents
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:
- 37% photon conversion before FCAL
- 99.6% efficiency for photons that reach 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) < .006 && fabs(phi_thrown - phi_recon) < .15)
Red/Black=% of photons that reach FCAL without converting:
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=
Above 1 GeV, 99.2% of uncoverted photons are reconstructed. This is less than the 99.6% reported for single photon sample, most likely this difference is due to photon showers overlapping with charged particle shower.
Below ~600 MeV, efficiency drops. This is due to showers contained within a single cell, which means no cluster is created.
Overall FCAL reconstruction efficiency considering only unconverted photons: 74%. Could be higher after trying to recover photons that convert.
Extra photon problem
To reduce number of extra "photons", consider a more aggressive matching of clusters to charged tracks:
- Only one matching FCAL cluster per track is allowed with the current code. Frequently hadronic showers are grouped into multiple clusters.
- The match radius is hardcoded as 5 cm, but in the calib/PID/photon_track_matching this parameter is set to 15 cm. Change this back to 15 cm.
Also use a timing cut (t_shower-t_flight) < 1.2 ns to cut out of out-of-time particles:
More aggressive cluster matching reduces average number of "photons" per event from 2.5 to 1.5. Timing cut on top of this reduces average to 1.2. (actually 0.77 photons should hit the FCAL per event)
This also reduces efficiency (as defined above) from 74% to 70%. Timing cut has negligible effect on efficiency.
