Azimuthal correlations between charged hadrons and direct photons at high-p$_{t}$ in $p+p$ and $Au+Au$ collisions at $\sqrt{s_{NN}}$ = 200 GeV

TL;DR

This paper reports on azimuthal correlations between high-energy direct photons and charged hadrons in proton-proton and gold-gold collisions at 200 GeV, aiming to understand medium effects on parton fragmentation.

Contribution

It presents new measurements of direct photon-hadron correlations over various centralities, providing insights into the medium's color charge density in heavy-ion collisions.

Findings

Per-trigger away-side yield of direct photons is smaller than from π0 triggers.

Correlations vary with collision centrality, indicating medium modification effects.

Results help constrain models of parton energy loss in quark-gluon plasma.

Abstract

Recent results at STAR for direct $\gamma$-charged hadron azimuthal correlations in heavy-ion collisions are presented. These correlations are used to study the color charge density of the medium through the medium-induced modification of high-p$_T$ parton fragmentation. Azimuthal correlations of direct photons at high transverse energy 8 $<$ E$_T$ $<$ 16 GeV with away-side charged hadrons of transverse momentum 3 $<$ p$_T$ $<$ 6 GeV/c have been measured over a broad range of centrality for $Au+Au$ collisions and $p+p$ collisions at $\sqrt{s_{NN}}$ = 200 GeV in the STAR experiment. The per-trigger away-side yield of direct $\gamma$ is smaller than from $\pi^{0}$ triggers in the same centrality class.