Difference between revisions of "Reconstruction, July 21, 2009"
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* Before χ^2 cuts ~50% of the generated signal events can be reconstructed. A cut on χ^2 < 3 leaves approximately 39% of generated events, | * Before χ^2 cuts ~50% of the generated signal events can be reconstructed. A cut on χ^2 < 3 leaves approximately 39% of generated events, | ||
* 10^7 Pythia hadronic background events were generated and then filtered by requiring that the total neutral energy be greater than 6GeV. 50,000 signal a2(1318) events were generated. This gives a ratio of cross-sections being 200:1 where the Pythia cross section at 9 GeV is 124 μb giving a cross section for the a2 to be ~0.6 μb. The 4 photon, 1 proton requirement leaves 12,690 background events and 24,870 signal events (5% more including 5 photon events). | * 10^7 Pythia hadronic background events were generated and then filtered by requiring that the total neutral energy be greater than 6GeV. 50,000 signal a2(1318) events were generated. This gives a ratio of cross-sections being 200:1 where the Pythia cross section at 9 GeV is 124 μb giving a cross section for the a2 to be ~0.6 μb. The 4 photon, 1 proton requirement leaves 12,690 background events and 24,870 signal events (5% more including 5 photon events). | ||
| + | *Protons (acceptance and smearing) are handle via HDParSim, a parametric Monte Carlo used as a plugin with the analysis code | ||
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| − | '''transverse momentum''' | + | '''Total transverse momentum (proton + 4γ)''' |
[[Image:PythiaA2 Pt.png|400px]] | [[Image:PythiaA2 Pt.png|400px]] | ||
Revision as of 22:30, 20 July 2009
Time: 11:00 EST/10:00 CST
- See GlueX Communications for detailed instructions
- ESNET Number 8542553
Documents to Review
- Reconstruction References
- Reconstruction document in progress
Tentative Agenda
- Generating Background Events (Pythia: 124 μb @ 9GeV beam energy)
- Reconstruction: Physics Reactions
Discussion
- Blake looked at his bggen folders to find that a BGGEN hddm file is ~1kB/event (10^7 events is ~10GB) and an HDGEANT hddm file (from filtered BGGEN events) is ~27kB/event. Filtering the data for neutral energy greater than 6GeV culled 80% of events. The final data set is after runnning though HDGEANT ~55GB for 2x10^6 events.
- Reconstruction
Reconstruction
- It is required that there are 4 or 5(~5% of accepted events) photons showers (none are due to charged particles - comparing swum tracks to shower positions), and 1 proton. This gives 6(30) possible combinations.
- Pi0 and Eta candidates are chosen as the eta-pi0 pair with the largest probability (from the TwoGammaFit )
- Before χ^2 cuts ~50% of the generated signal events can be reconstructed. A cut on χ^2 < 3 leaves approximately 39% of generated events,
- 10^7 Pythia hadronic background events were generated and then filtered by requiring that the total neutral energy be greater than 6GeV. 50,000 signal a2(1318) events were generated. This gives a ratio of cross-sections being 200:1 where the Pythia cross section at 9 GeV is 124 μb giving a cross section for the a2 to be ~0.6 μb. The 4 photon, 1 proton requirement leaves 12,690 background events and 24,870 signal events (5% more including 5 photon events).
- Protons (acceptance and smearing) are handle via HDParSim, a parametric Monte Carlo used as a plugin with the analysis code
π0 mass: the lines in black are Pythia + signal events, red are cutting on χ^2 < 3, green is Pythia background only cut on χ^2 < 3.
η mass: the lines in black are Pythia + signal events, red are cutting on χ^2 < 3,, green is Pythia background only cut on χ^2 < 3.
resonance mass
- a2(1318) resonance with angular distribution from IU generator.
Total transverse momentum (proton + 4γ)
