Isolation of flow and nonflow correlations by two- and four-particle cumulant measurements of azimuthal harmonics in √s[subscript NN] = 200 GeV Au+Au collisions

Abstract

A data-driven method was applied to Au+Au collisions a t√s[subscript NN] = 200 GeV made with the STAR detector at RHIC to isolate pseudorapidity distance Δη-dependent and Δη-independent correlations by using two- and four-particle azimuthal cumulant measurements. We identified a Δη-independent component of the correlation, which is dominated by anisotropic flow and flow fluctuations. It was also found to be independent of η within the measured range of pseudorapidity |η| < 1. In 20–30% central Au+Au collisions, the relative flow fluctuation was found to be 34% ± 2%(stat.) ± 3%(sys.) for particles with transverse momentum [subscript pT] less than 2 GeV/c. The Δη-dependent part, attributed to nonflow correlations, is found to be 5% ± 2%(sys.) relative to the flow of the measured second harmonic cumulant at |Δη| > 0.7.