Measurements of Fragmentation Photons with the PHENIX Detector

Abstract

Direct photons associated with jets provide a direct measurement of the effects of energy loss on the fragmentation of the parton as it propagates through the medium. Perturbative QCD calculations describe the direct photon cross section well at next-to-leading order, predicting a significant contribution from photons produced through parton fragmentation. Non-perturbative quantities such as the photon fragmentation function, which is poorly constrained, lead to large theoretical uncertainties. The measurement of photons correlated with jets in p+p collisions serves as an important test of these calculations and is an essential baseline measurement for comparison to A+A collisions. A natural way of selecting such photons is to study hadron-photon correlations. Results for the production of photons associated with high pT hadron triggers are presented for PHENIX p+p data at 200 GeV center-of-mass energy.