Evolution of fluctuations in the initial state of heavy-ion collisions from RHIC to LHC

TL;DR

This paper analyzes how initial state fluctuations in heavy-ion collisions evolve from RHIC to LHC energies, using an analytical model based on the color glass condensate theory that matches experimental data.

Contribution

It introduces an analytical description of initial energy-density fluctuations based on CGC theory that explains the energy dependence of observed fluctuations.

Findings

Fluctuations are larger at RHIC than at LHC energies.

The CGC-based model accurately predicts the energy evolution of fluctuations.

Fluctuations scale inversely with the saturation scale of the nuclei.

Abstract

Fluctuations in the initial state of heavy-ion collisions are larger at RHIC energy than at LHC energy. This fact can be inferred from recent measurements of the fluctuations of the particle multiplicities and of elliptic flow performed at the two different energies. We show that an analytical description of the initial energy-density field and its fluctuations motivated by the color glass condensate (CGC) effective theory predicts and quantitatively captures the measured energy evolution of these observables. The crucial feature is that fluctuations in the CGC scale like the inverse of the saturation scale of the nuclei.