Fluctuating Glasma initial conditions and flow in heavy ion collisions

TL;DR

This paper develops a detailed model of initial conditions in heavy-ion collisions using the CGC framework, incorporating quantum fluctuations and energy fluctuations, and compares the resulting flow observables with experimental data.

Contribution

It introduces an IP-Glasma model that combines impact parameter dependent saturation with classical Yang-Mills fields, including quantum fluctuations, to better describe initial energy fluctuations and flow in heavy-ion collisions.

Findings

Initial energy fluctuations follow a negative binomial distribution.

The ratio of triangularity to eccentricity aligns with experimental flow data.

Transverse momentum spectra and flow coefficients are consistent with observations.

Abstract

We compute initial conditions in heavy-ion collisions within the Color Glass Condensate (CGC) framework by combining the impact parameter dependent saturation model (IP-Sat) with the classical Yang-Mills description of initial Glasma fields. In addition to fluctuations of nucleon positions, this IP-Glasma description includes quantum fluctuations of color charges on the length-scale determined by the inverse nuclear saturation scale Q_s. The model naturally produces initial energy fluctuations that are described by a negative binomial distribution. The ratio of triangularity to eccentricity is close to that in a model tuned to reproduce experimental flow data. We compare transverse momentum spectra and v_(2,3,4)(p_T) of pions from different models of initial conditions using relativistic viscous hydrodynamic evolution.