Direct Photon-Hadron Correlations Measured with PHENIX

TL;DR

This paper reports on measurements of direct photon-hadron correlations in heavy-ion collisions using PHENIX, which help understand jet quenching and medium modifications in quark-gluon plasma.

Contribution

It presents new high-precision measurements of direct photon-hadron correlations at RHIC, comparing results with p+p data and theoretical models to study energy loss effects.

Findings

Enhanced statistical precision in Au+Au collisions

Comparison with p+p results shows medium modification

Agreement with energy loss models

Abstract

Direct photon-hadron correlations greatly improve our ability to perform jet tomography in heavy-ion collisions because the momentum of the direct photon can be used to constrain the initial momentum of the opposing jet. By comparing the spectrum of away-side hadrons observed in heavy ion collisions to the spectrum seen in nucleon collisions we can quantify the medium modification to the fragmentation function due to energy loss of the away-side parton. High $p_{T}$ direct photon-hadron correlations have been measured with the PHENIX detector using a statistical subtraction method to remove the photon contribution from meson decays. The increased integrated luminosity in the most recent Au+Au RHIC run at $\sqrt{s_{NN}}$ = 200 GeV provides substantially improved statistical precision and enhances the kinematic reach. These measurements are compared to PHENIX p+p results and several theoretical models of energy loss. In addition, we compare direct photon-hadron and $\pi^{0}$-hadron correlations.