Ilya Selyuzhenkov January 20, 2009

Note:
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

Comments

• 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)

Figures

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