Relating Eccentricity Fluctuations to Density Fluctuations in Heavy-ion Collisions

Abstract

The magnitude of anisotropic flow in a nucleus-nucleus collision is determined by the energy-density field, rho(x; y; z), created right after the collision occurs. Specifically, elliptic flow, v(2), and triangular flow, v(3), are proportional to the anisotropy coefficients epsilon(2) and epsilon(3), which are functionals of rho. We express the mean and the variance of epsilon(2) and epsilon(3) as a function of the 1- and 2-point functions of rho. These results generalize results obtained previously that were valid only for central collisions or only for identical point-like sources. We apply them to the color glass condensate effective theory using the recently derived expression of the 2-point function.