2009.01.08 Away side jet pt vs. photon pt

Ilya Selyuzhenkov January 08, 2009

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


(concentrated on pre-shower1>0 case
which has better statistics for QCD Monte-Carlo):

  • Fig.1, lower plots
    Vertex z distributions from QCD MC and pp2006 data are different in the negative region
  • Fig.2, lower plots
    For the away side jet pt < 8GeV region
    QCD Monte-Carlo underestimates the data.
  • Fig.4, lower plots
    gamma-jet pt asymmetry plot shows
    that in QCD MC photon and jet pt's are better correlated than in the data
  • Fig.5, lower plots
    Most of the differences between QCD MC and pp2006 data for pre-shower1>0 case
    are probably from the lower gamma and jet pt region


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)