Transport coefficients of strongly interacting quark-gluon plasma including elastic and inelastic scattering within the dynamical quasiparticle model

Abstract

We study the impact of inelastic gluon-radiation and absorption processes on the transport coefficients of the quark-gluon plasma within the dynamical quasiparticle model (DQPM) in the temperature--baryon-chemical-potential plane $(T,\mu_B)$. Extending the $2\rightarrow2$ baseline established in previous DQPM calculations, we include gluon-radiation $2\rightarrow3$ and the inverse gluon-absorption $3\rightarrow2$ scattering channels with massive partons and effective DQPM propagators and vertices. The corresponding momentum-dependent interaction rates and relaxation times are used to calculate the shear viscosity, bulk viscosity, electric conductivity, and baryon diffusion coefficient as functions of temperature $T$ and baryon chemical potential $\mu_B$. Within the relaxation time approximation, we find that $2\leftrightarrow3$ contributions systematically reduce all considered transport coefficients relative to the $2\rightarrow2$ only results, in accordance with the decrease of the relaxation times. In the thermal regime explored here, however, this reduction remains moderate, since the investigated inelastic rates stay below the $2\rightarrow2$ ones over the considered $(T,\mu_B)$ range. The inelastic channels become more relevant mainly for partonic scatterings at large momenta, which are thermally suppressed in the strongly interacting QGP. At $\mu_B=0$, the resulting $\eta/s$, $\zeta/s$, and $\sigma_Q/T$ are compatible with available lattice-QCD estimates within uncertainties. At finite $\mu_B$, our results provide predictions for the transport properties of QCD matter relevant for beam-energy-scan programs.