The Rise and Fall of the Ridge

TL;DR

This paper explains the centrality-dependent ridge-like correlations observed in heavy ion collisions at RHIC by linking initial coordinate space fluctuations to final momentum correlations, offering new insights into collision dynamics.

Contribution

It introduces a framework connecting initial density fluctuations to final momentum correlations, using the ratio v_n^2/ε_{n,part}^2 to analyze collision behavior.

Findings

Correlation amplitude peaks at mid-central collisions

Initial fluctuations drive the observed ridge structure

The proposed ratio helps understand collision dynamics

Abstract

Recent data from heavy ion collisions at RHIC show unexpectedly large near-angle correlations that broaden longitudinally with centrality. The amplitude of this ridge-like correlation rises rapidly with centrality, reaches a maximum, and then falls in the most central collisions. In this talk we explain how this behavior can be easily understood in a picture where final momentum-space correlations are driven by initial coordinate space density fluctuations. We propose $v_n^2/\epsilon_{n,part}^{2}$ as a useful way to study these effects and explain what it tells us about the collision dynamics.