Energy and system-size dependence of two- and four-particle v2 measurements in heavy-ion collisions at √sNN=62.4 and 200 GeV and their implications on flow fluctuations and nonflow

Abstract

We present STAR measurements of azimuthal anisotropy by means of the two- and four-particle cumulants v2 (v2{2} and v 2{4}) for Au+Au and Cu+Cu collisions at center-of-mass energies √sNN=62.4 and 200 GeV. The difference between v 2{2}2 and v2{4 }2 is related to v2 fluctuations (σv2) and nonflow (δ2). We present an upper limit to σv 2/v2. Following the assumption that eccentricity fluctuations σ dominate v2 fluctuations σv 2v2≈σ we deduce the nonflow implied for several models of eccentricity fluctuations that would be required for consistency with v2{2} and v2{4}. We also present results on the ratio of v2 to eccentricity. © 2012 American Physical Society.