On the origin of trigger-angle dependence of di-hadron correlations

TL;DR

This paper explains the trigger-angle dependence of di-hadron correlations in heavy-ion collisions using hydrodynamic simulations and a one-tube model, aligning well with experimental STAR data.

Contribution

It introduces a hydrodynamic calculation of di-hadron correlations as functions of trigger angle and momentum, and interprets the results with a one-tube model considering flow effects.

Findings

Hydrodynamic simulations reproduce the observed correlation patterns.

The trigger-angle dependence is explained by interplay of flow and fluctuations.

Results agree reasonably with STAR experimental data.

Abstract

The STAR Collaboration reported measurements of di-hadron azimuthal correlation in medium-central Au+Au collisions at 200 A$\,$GeV, where the data are presented as a function of the trigger particle's azimuthal angle relative to the event plane $\phi_s $. In particular, it is observed that the away-side correlation evolves from single- to double-peak structure with increasing $\phi_s$. In this work, we present the calculated correlations as functions of both $\phi_s$ and particle transverse momentum $p_T $, using the hydrodynamic code NeXSPheRIO. The results are found to be in reasonable agreement with the STAR data. We further argue that the above $\phi_s$ dependence of the correlation structure can be understood in terms of one-tube model, as due to an interplay between the background elliptic flow caused by the initial state global geometry and the flow produced by fluctuations.