Exposing the Noncollectivity in Elliptic Flow

TL;DR

This paper proposes a new observable based on backward-forward elliptic anisotropy correlation to differentiate between collective flow and non-collective effects in elliptic flow measurements in heavy ion collisions.

Contribution

It introduces an experimentally accessible observable that can identify the transition point from collective to non-collective dominance in elliptic anisotropy.

Findings

The observable distinguishes collective from non-collective contributions.

It identifies the momentum scale where collective expansion begins.

It helps understand the dominance of hard processes in elliptic anisotropy.

Abstract

We show that backward-forward elliptic anisotropy correlation provides an experimentally accessible observable which distinguishes between collective and non-collective contributions to the observed elliptic anisotropy $v_2$ in relativistic heavy ion collisions. The measurement of this observable will reveal the momentum scale at which collective expansion seizes and where the elliptic anisotropy is dominated by (semi)-hard processes.