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

摘要

A data-driven method was applied to Au+Au collisions atsNN=200?GeVmade 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 ofηwithin the measured range of pseudorapidity|η|<1. In 20–30% central Au+Au collisions, the relative flow fluctuation was found to be34%±2%(stat.)±3%(sys.)for particles with transverse momentumpTless than2GeV/c. The Δη-dependent part, attributed to nonflow correlations, is found to be5%±2%(sys.)relative to the flow of the measured second harmonic cumulant at|Δη|>0.7.