Extracting gamma-jet cross section at forward rapidity from pp@200GeV collisions

Analysis overview

1. Data samples, event selection, luminosity determination
2. Isolating photon-jet events
   • Transverse shower shape analysis
   • Isolation cuts
   • Cut optimization
3. Trigger effects study
4. Data to Monte-Carlo comparison/normalization and raw yields
5. Acceptance/efficiency corrections
6. Corrected yields
7. Background subtraction
8. Systematic uncertainties
9. Comparison with theory

Data samples, event selection, luminosity determination

Real data, and signal/background Monte-Carlo samples:

• pp@200GeV collisions, STAR produnctionLong.
  Trigger: eemc-http-mb-L2gamma [id:137641] (L ~ 3.164 pb^1)

• Pythia prompt photon (signal) Monte-Carlo sample.
  Filtered Prompt Photon p6410EemcGammaFilter.
  Partonic pt range 2-25 GeV.

• Pythia 2->2 hard QCD processes (background) Monte-Carlo sample.
  Filtered QCD p6410EemcGammaFilter.
  Partonic pt range 2-25 GeV.

Isolating photon-jet events

1. Shower shape analysis
   • Shower shapes
   • Sided residual analysis
2. Isolation cuts
   • Energy clustering (2x1 vs. 2x2 vs. 3x3, cluster energy vs. rapidity)
   • Charge particle veto
   • photon and jet pt balance
   • Tower multiplicity
3. Cut optimization with LDA.
   Input variables (list can be expanded):
   • Energy fraction in 3x3 cluster within a r=0.7 radius, E_3x3/E_0.7
   • Photon-jet pt balance, [pt_gamma-pt_jet]/pt_gamma
   • Number of charge tracks within r=0.7 around gamma candidate
   • Number of Endcap towers fired within r=0.7 around gamma candidate
   • Number of Barrel towers fired within r=0.7 around gamma candidate
   • Shower shape analysis: distance to 80% cut line
   • Energy fraction in E_2x1 and E_2x2 witin E_3x3
   • Energy in post-shower layer under 3x3 tower patch
   • Tower energy in 3x3 patch
   • SMD-u/v energy in 25 central strips
   • SMD-u/v peak energy (in 5 central strips)

Trigger effects study

No studies yet

• Trigger effects vs pt
• Trigger effects vs eta
• What else?

Data to Monte-Carlo comparison/normalization and raw yields

• Overall data to MC normalization based on vertex z distribution
• Data to MC comparison of raw yield in various detector subsystems
• Uncorrected yields optimized with different efficiency/purity

Acceptance/efficiency corrections

No studies yet

• What needs to be studied for acceptance/efficiency effects?
• Converting reconstructed photon (jet) energy/momentum to the true one
• Reconstruction efficiency vs. rapidity, pt, etc

Corrected yields

No studies yet

• Produce acceptance/efficiency corrected yields

Background subtraction

No studies yet

• Statistical background subtraction based on Pythia+GEANT Monte-Carlo
• Estimate systematic uncertainties due to background subtraction

Systematic uncertainties

No studies yet

• Calorimeter energy resolution
• Trigger bias
• Other effects

Comparison with theory

No comparison yet

• Request for pQCD calculations at forward rapidity