The importance of the bulk viscosity of QCD in ultrarelativistic heavy-ion collisions

TL;DR

This paper demonstrates that including bulk viscosity in simulations of heavy-ion collisions at LHC energies significantly improves agreement with experimental data, aiding the determination of QCD transport coefficients.

Contribution

It introduces the impact of nonzero bulk viscosity on heavy-ion collision observables and shows improved simulation-data agreement.

Findings

Bulk viscosity enhances the match between simulations and experimental data.

Including bulk viscosity affects transverse momentum spectra and azimuthal anisotropy.

Results support the extraction of QCD transport coefficients from experimental data.

Abstract

We investigate the consequences of a nonzero bulk viscosity coefficient on the transverse momentum spectra, azimuthal momentum anisotropy, and multiplicity of charged hadrons produced in heavy ion collisions at LHC energies. The agreement between a realistic 3D hybrid simulation and the experimentally measured data considerably improves with the addition of a bulk viscosity coefficient for strongly interacting matter. This paves the way for an eventual quantitative determination of several QCD transport coefficients from the experimental heavy ion and hadron-nucleus collision programs.