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
  2. Isolation cuts
  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
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