Title

Gamma-jet cross sections for forward gammas in proton-proton collisions at root(s) = 200 GeV/c

Principal Authors (alphabetical order)

Keith Krueger (ANL), Hal Spinka (ANL), Dave Underwood (ANL)

Intended Journal

Physical Review D

Abstract

A measurement is presented of the cross section vs. transverse momentum (pT) for gamma + jet production in proton-proton collisions. The data were measured in the STAR detector at RHIC at √s = 200 GeV/c. The jet was detected at central pseudorapidity (|η| < 0.8) and the γ at intermediate pseudorapidity (1.2 < η < 2.0). These regions were chosen to access lower x of the gluon relative to a central-pseudorapidity-only measurement, and also because a large partonic spin asymmetry, All, in the parton cm is selected. The technique of finding single γ’s in the background of photons from π0 decay is based on a standard chi-squared method for the shower shape in the shower maximum detector of an electromagnetic calorimeter.

Outline

• Introduction
  • Refs. to earlier measurements and theory predictions
  • Connection to gluon distribution
• Hardware
  • RHIC general (Refs.)
  • STAR general (Refs.)
  • TPC and BEMC for jets (Refs.)
  • EEMC and ESMD for gamma
  • trigger
  • luminosity
• Analysis
  • Jets (Refs.)
  • Gammas with chi-squared (Ref.)
  • Efficiency / RooUnfold
  • Other Corrections?
  • Systematics
  • Table of results with errors
• Results
  • Comparison to JETPHOX (Refs.)
  • Comparison to pi0’s?
• Summary / Conclusions

Presentations to the Spin PWG (April 23)

• Methodology
• Systematics