Exploring the centrality dependence of elliptic and triangular flows

TL;DR

This paper models initial state eccentricities in heavy ion collisions using a Color Glass Condensate framework, successfully describing flow data and elucidating how eccentricities relate to collision geometry and fluctuations.

Contribution

It introduces a model based on the Color Glass Condensate that accurately predicts elliptic and triangular flow harmonics across centralities in heavy ion collisions.

Findings

Model describes ALICE and ATLAS data well

Eccentricity $ ext{ε}_2$ linked to collision geometry

Eccentricity $ ext{ε}_3$ driven by fluctuations

Abstract

A detailed study of elliptical and triangular eccentricities in the initial state of relativistic heavy ion collisions is presented. A model of randomly distributed sources of energy density in the transverse plane based on the effective theory of Color Glass Condensate is used. This model describes well the ALICE and ATLAS data for Pb+Pb collisions at center-of-mass energy 5.02 TeV per nucleon pair in a wide range of centralities, if the second $v_2$ and third $v_3$ harmonics of the anisotropic flow are simply implied to be proportional to the eccentricities $\varepsilon_2$ and $\varepsilon_3$ as a reasonable approximation. The eccentricity $\varepsilon_2$ is closely related with the collision geometry and its centrality dependence is mainly determined by the edge diffuseness of the region of the uniform distribution of the saturation pulse of the oncoming nucleus. The eccentricity $\varepsilon_3$ is completely determined by the chaotic fluctuations of the source position in the region of overlapping nuclei and is substantially dependent on the overlap area only.