System size dependence of associated yields in hadron-triggered jets

TL;DR

This study investigates how the size of the colliding system affects jet-like correlations in high-energy nuclear collisions, revealing similar near-side yields but varying away-side suppression across different systems and centralities.

Contribution

It provides new measurements of jet suppression patterns across different collision systems and compares them with theoretical models to constrain medium properties.

Findings

Near-side jet-like correlations are similar across systems.

Away-side suppression depends on system size and centrality.

Data challenges existing theoretical models.

Abstract

We present results on the system size dependence of high transverse momentum di-hadron correlations at $\sqrt{s_{NN}}$ = 200 GeV as measured by STAR at RHIC. Measurements in d+Au, Cu+Cu and Au+Au collisions reveal similar jet-like correlation yields at small angular separation ($\Delta\phi\sim0$, $\Delta\eta\sim0$) for all systems and centralities. Previous measurements have shown that the away-side yield is suppressed in heavy-ion collisions. We present measurements of the away-side suppression as a function of transverse momentum and centrality in Cu+Cu and Au+Au collisions. The suppression is found to be similar in Cu+Cu and Au+Au collisions at a similar number of participants. The results are compared to theoretical calculations based on the parton quenching model and the modified fragmentation model. The observed differences between data and theory indicate that the correlated yields presented here will provide important constraints on medium density profile and energy loss model parameters.