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

A data-driven method was applied to Au+Au collisions at sNN=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|η|<1. In 20–30% central Au+Au collisions, the relative flow fluctuation was found to be 34%±2%(stat.)±3%(sys.)34%±2%(stat.)±3%(sys.) for particles with transverse momentum pTpT less than 2 GeV/c2 GeV/c. The Δη  -dependent part, attributed to nonflow correlations, is found to be 5%±2%(sys.)5%±2%(sys.) relative to the flow of the measured second harmonic cumulant at |Δη|>0.7|Δη|>0.7.