PHENIX results on jet modification with π0- and photon-triggered two particle correlations in p+p, p(d)+Au, and Au+Au collisions

Abstract

As a colorless probe, direct photons balance the pT of the away-side jet at leading order. Direct photon-hadron correlations are thus an excellent probe for nuclear structure and QCD effects, including parton energy loss in the Quark-Gluon Plasma. PHENIX has measured π0 and direct photon-triggered two-particle azimuthal correlations in a variety of collision systems ranging from p+p to Au+Au at 200 GeV. In p+Au and d+Au collisions, no modification of the per-trigger jet yield or away-side correlation width compared to p+p collisions is observed for direct photon triggered correlations while an increase in the away-side width for π0 triggered correlations in p+Au has been measured. In Au+Au collisions, direct photons have been identified statistically as well as using an isolation cut. Combining data sets from different collision systems allows us to quantify the transition from suppression at high zT(pT,h/pT,γ) to the enhancement of low zT particles relative to p+p, and to study this transition as a function of trigger pT.