Effects of Momentum Conservation and Flow on Angular Correlations at RHIC

TL;DR

This paper investigates how momentum conservation and collective flow influence azimuthal correlations at RHIC, highlighting their significant contributions and limitations in explaining observed phenomena related to parity fluctuations.

Contribution

It demonstrates that momentum conservation and elliptic flow significantly affect azimuthal correlations, providing a crude simulation to analyze their impact and identify the need for more comprehensive models.

Findings

Momentum conservation and flow contribute notably to correlations.

Crude pion gas simulation reproduces correlation scale.

Centrality dependence suggests additional effects beyond the model.

Abstract

Correlations of azimuthal angles observed at RHIC have gained great attention due to the prospect of identifying fluctuations of parity-odd regions in the field sector of QCD. Whereas the observable of interest related to parity fluctuations involves subtracting opposite-sign from same-sign correlations, the STAR collaboration reported the same-sign and opposite-sign correlations separately. It is shown here how momentum conservation combined with collective elliptic flow contributes significantly to this class of correlations, though not to the difference between the opposite- and same-sign observables. The effects are modeled with a crude simulation of a pion gas. Though the simulation reproduces the scale of the correlation, the centrality dependence is found to be sufficiently different in character to suggest additional considerations beyond those present in the pion gas simulation presented here.