Shear Viscosity of Collider-Produced QCD Matter II: Comparing a Multi-Component Chapman-Enskog Framework with AMPT in Full Equilibrium

TL;DR

This paper develops a multi-component Chapman-Enskog framework to analyze the shear viscosity of QGP, incorporating species-specific effects and comparing results with a transport model, enhancing understanding of QGP transport properties.

Contribution

It introduces a novel multi-component Chapman-Enskog approach that includes quark and gluon contributions and compares it with existing transport models for the first time.

Findings

Shear viscosity and η/s increase with quark and gluon contributions.

Both η and η/s decrease over time due to cooling and expansion.

Results are consistent with perturbative QCD predictions.

Abstract

Transport properties of the quark-gluon plasma are instrumental to testing perturbative quantum chromodynamics and understanding the extreme conditions of relativistic heavy-ion collisions. This study presents an analytical investigation of the shear viscosity $\eta$ and the shear viscosity-to-entropy density ratio $\eta/s$ of the QGP using a novel multi-component Chapman-Enskog framework assuming full thermalization. The approach incorporates species-specific contributions from gluons and (anti-)quarks into the plasma shear viscosity, temperature-dependent running parameters for the Debye mass and strong coupling, and a time-dependent cooling model. Our findings show that both $\eta$ and $\eta/s$ are enhanced by the inclusion of (anti-)quarks with gluons, and the parameters decrease over time due to the cooling and expansion of the QGP. These results align with perturbative QCD predictions, offering a more optimistic representation of QGP transport properties under dynamic conditions. This multi-component framework is compared with a multi-phase transport model that treats the QGP as a gluon gas with (anti-)quark augmentation.