Spatial anisotropy: a method to study anisotropic flow in heavy ion collisions

Abstract

We introduce a method to study anisotropic flow parameter vn as a collective probe to Quark Gluon Plasma in relativistic heavy ion collisions. The emphasis is put on the use of the Fourier expansion of initial spatial azimuthal distributions of participant nucleons in the overlapped region. The coefficients ∊n of Fourier expansion are called the spatial anisotropy parameter for the n-th harmonic. We propose that collective dynamics can be studied by vn/∊n. In this paper, we will discuss in particular the second (n = 2) and the fourth (n = 4) harmonics.