Event-by-event fluctuations of azimuthal particle anisotropy in Au+Au collisions at sqrt(s_NN) = 200 GeV

TL;DR

This study measures event-by-event fluctuations of elliptic flow in Au+Au collisions at 200 GeV, providing insights into initial state fluctuations and constraining hydrodynamic models of heavy ion collisions.

Contribution

First measurement of elliptic flow fluctuations in Au+Au collisions at 200 GeV, establishing an upper limit and linking results to initial nucleon spatial fluctuations.

Findings

Elliptic flow fluctuations are approximately 40%.

Results are consistent with initial spatial fluctuation models.

Provides constraints for hydrodynamic evolution models.

Abstract

This paper presents the first measurement of event-by-event fluctuations of the elliptic flow parameter v_2 in Au+Au collisions at sqrt(s_NN) = 200GeV as a function of collision centrality. The relative non-statistical fluctuations of the v_2 parameter are found to be approximately 40%. The results, including contributions from event-by-event elliptic flow fluctuations and from azimuthal correlations that are unrelated to the reaction plane (non-flow correlations), establish an upper limit on the magnitude of underlying elliptic flow fluctuations. This limit is consistent with predictions based on spatial fluctuations of the participating nucleons in the initial nuclear overlap region. These results provide important constraints on models of the initial state and hydrodynamic evolution of relativistic heavy ion collisions.