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 v2{4}) for Au+Au and Cu+Cu collisions at center-of-mass energies √sNN=62.4 and 200 GeV. The difference between v2{2}2 and v2{4}2 is related to v2 fluctuations (σv2) and nonflow (δ2). We present an upper limit to σv2/v2. Following the assumption that eccentricity fluctuations σɛ dominate v2 fluctuations σv2/v2≈σɛ/ɛ 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.