2009.01.20 Away side jet pt vs. photon pt: more stats for QCD pt_parton 9-15GeV

Ilya Selyuzhenkov January 20, 2009

this is an update with 10x more statitstics for QCD 9-15GeV parton pt bin.
See this post for old results.

Data sets

  • pp2006 - STAR 2006 pp longitudinal data (~ 3.164 pb^1)
    Trigger: eemc-http-mb-L2gamma [id:137641]
  • gamma-jet[gamma-filtered] - data-driven Prompt Photon [p6410EemcGammaFilter] events.
    Partonic pt range 2-25 GeV.
  • QCD jets[gamma-filtered] - data-driven QCD [p6410EemcGammaFilter] events.
    Partonic pt range 2-25 GeV.

Cuts applied

  • Di-jet events
  • Require to reconstruct photon momentum (no gamma-jet isolation cuts)
  • Gamma pt > 7GeV
  • L2gamma emulation in Monte-Carlo
  • L2gamma triggered pp2006 events


  • Vertex z distributions from QCD MC and pp2006 data
    are different in the negative region (see Fig.1)
  • pp2006 data to Monte-Carlo ratio
    does not depends on reconstructed photon pt,
    but it has some vertex z dependence
    (see data to MC ratio in Fig.6 for pre-shower1 > 4MeV case)


Figure 1: Vertex z distribution

Figure 2: Away side jet pt

Figure 3: Photon pt

Figure 4: gamma-jet pt asymmetry: (pt_gamma - pt_jet)/pt_gamma

Figure 5: gamma pt vs. away side jet pt
1st column: triggered pp2006 data
2nd column: gamma-jet MC (l2gamma trigger on)
3rd column: QCD background MC (l2gamma trigger on)

Data to Monte_Carlo normalization

Figure 6: pp2006 data to Monte -Carlo sum [QCD + gamma-jet] ratio
for pre-shower1>4MeV (most of statistics)
Left: data to MC ratio vs. reconstructed gamma pt.
Solid line shows constant line fit (p0 ~ 1.3)
Right: data to MC ratio vs. reconstructed vertex position