Energy loss, equilibration, and thermodynamics of a baryon rich strongly coupled quark-gluon plasma

TL;DR

This paper develops a holographic model based on lattice QCD data to study the thermodynamics, energy loss, and thermalization of a baryon-rich strongly coupled quark-gluon plasma, revealing nontrivial density and temperature effects.

Contribution

It introduces a holographic framework calibrated with lattice data to analyze both equilibrium and out-of-equilibrium properties of baryon-rich QGP, including energy loss and thermalization behaviors.

Findings

Quantitative agreement with lattice data for pressure and speed of sound at μ_B ≤ 400 MeV.

Energy loss of quarks increases with baryon density and varies rapidly near the crossover.

Thermalization time decreases in dense baryonic medium.

Abstract

Lattice data for the QCD equation of state and the baryon susceptibility near the crossover phase transition (at zero baryon density) are used to determine the input parameters of a 5-dimensional Einstein-Maxwell-Dilaton holographic model that provides a consistent holographic framework to study both equilibrium and out-of-equilibrium properties of a hot and {\it baryon rich} strongly coupled quark-gluon plasma (QGP). We compare our holographic equation of state computed at nonzero baryon chemical potential, $\mu_B$, with recent lattice calculations and find quantitative agreement for the pressure and the speed of sound for $\mu_B \leq 400$ MeV. This holographic model is used to obtain holographic predictions for the temperature and $\mu_B$ dependence of the drag force and the Langevin diffusion coefficients associated with heavy quark jet propagation as well as the jet quenching parameter $\hat{q}$ and the shooting string energy loss of light quarks in the baryon dense plasma. We find that the energy loss of heavy and light quarks generally displays a nontrivial, fast-varying behavior as a function of the temperature near the crossover. Moreover, energy loss is also found to generally increase due to nonzero baryon density effects even though this strongly coupled liquid cannot be described in terms of well defined quasiparticle excitations. Furthermore, to get a glimpse of how thermalization occurs in a hot and baryon dense QGP, we study how the lowest quasinormal mode of an external massless scalar disturbance in the bulk is affected by a nonzero baryon charge. We find that the equilibration time associated with the lowest quasinormal mode decreases in a dense medium.