Eccentricity fluctuations and elliptic flow at RHIC

Abstract

Fluctuations in nucleon positions can affect the spatial eccentricity of the overlap zone in nucleus–nucleus collisions. We show that elliptic flow should be scaled by different eccentricities depending on which method is used for the flow analysis. These eccentricities are estimated semi-analytically. When v2 is analyzed from 4-particle cumulants, or using the event plane from directed flow in a zero-degree calorimeter, the result is shown to be insensitive to eccentricity fluctuations.