Measurement of direct photon production in p + p collisions at sqrt(s) = 200 GeV

TL;DR

This paper reports measurements of direct photon production in proton-proton collisions at 200 GeV, comparing results with perturbative QCD predictions and examining photon isolation effects.

Contribution

It provides the first detailed measurement of direct photon cross sections at RHIC energies and tests pQCD predictions including photon isolation criteria.

Findings

pQCD describes data well for p_T > 5 GeV/c

Isolated photon fraction matches pQCD for p_T > 7 GeV/c

Measurement uncertainties are comparable to theoretical ones

Abstract

Cross sections for mid-rapidity production of direct photons in p+p collisions at the Relativistic Heavy Ion Collider (RHIC) are reported for 3 < p_T < 16 GeV/c. Next-to-leading order (NLO) perturbative QCD (pQCD) describes the data well for p_T > 5 GeV/c, where the uncertainties of the measurement and theory are comparable. We also report on the effect of requiring the photons to be isolated from parton jet energy. The observed fraction of isolated photons is well described by pQCD for p_T > 7 GeV/c.