Azimuthal di-hadron correlations in d+Au and Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV from STAR

TL;DR

This study examines azimuthal di-hadron correlations in d+Au and Au+Au collisions at 200 GeV, revealing jet fragmentation at high transverse momentum and additional particle production mechanisms at lower transverse momentum, with broadening and softening effects in Au+Au.

Contribution

It provides detailed measurements of di-hadron correlations across different collision systems and transverse momenta, highlighting the transition from jet fragmentation to other production mechanisms in heavy-ion collisions.

Findings

Jet fragmentation dominates at high extit{p}_T in both systems.

Enhanced near- and away-side yields at low extit{p}_T in Au+Au.

Broadening and softening of away-side correlations in Au+Au.

Abstract

Yields, correlation shapes, and mean transverse momenta \pt{} of charged particles associated with intermediate to high-\pt{} trigger particles ($2.5 < \pt < 10$ \GeVc) in d+Au and Au+Au collisions at $\snn=200$ GeV are presented. For associated particles at higher $\pt \gtrsim 2.5$ \GeVc, narrow correlation peaks are seen in d+Au and Au+Au, indicating that the main production mechanism is jet fragmentation. At lower associated particle $\pt < 2$ \GeVc, a large enhancement of the near- ($\dphi \sim 0$) and away-side ($\dphi \sim \pi$) associated yields is found, together with a strong broadening of the away-side azimuthal distributions in Au+Au collisions compared to d+Au measurements, suggesting that other particle production mechanisms play a role. This is further supported by the observed significant softening of the away-side associated particle yield distribution at $\dphi \sim \pi$ in central Au+Au collisions.