The STAR Collaboration reported measurements of di-hadron azimuthal correlations 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 ${\varphi }_s$. In particular, it is observed that the away-side correlation evolves from a single- to a double-peak structure with increasing ${\varphi }_s$. In this work, we present the calculated correlations as functions of both ${\varphi }_s$ and the 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 ${\varphi }_s$ dependence of the correlation structure can be understood in terms of the 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.

• Received 29 July 2012

DOI:https://doi.org/10.1103/PhysRevC.87.014904