Extracting the bulk viscosity of the quark-gluon plasma

TL;DR

This paper studies how a nonzero bulk viscosity affects flow anisotropy in ultracentral heavy ion collisions, finding that including bulk viscosity improves data agreement and allows extraction of optimal viscosity values.

Contribution

It introduces a method to extract bulk viscosity of quark-gluon plasma from flow harmonic data in ultracentral collisions, enhancing understanding of QGP properties.

Findings

Finite bulk viscosity improves flow harmonic descriptions.

Optimal viscosity coefficients are extracted for best data fit.

Bulk viscosity significantly influences ultracentral collision dynamics.

Abstract

We investigate the implications of a nonzero bulk viscosity coefficient on the azimuthal momentum anisotropy of ultracentral relativistic heavy ion collisions at the Large Hadron Collider. We find that, with IP-Glasma initial conditions, a finite bulk viscosity coefficient leads to a better description of the flow harmonics in ultracentral collisions. We then extract optimal values of bulk and shear viscosity coefficients that provide the best agreement with flow harmonic coefficients data in this centrality class.