Gauge-invariant screening masses and static quark free energies in $N_f = 2+1$ QCD at non-zero baryon density

TL;DR

This paper extends the concept of gauge-invariant screening masses and static quark free energies in the Quark-Gluon Plasma to finite baryon density, providing lattice results that show their dependence on chemical potential and temperature.

Contribution

It introduces a method to define gauge-invariant screening masses at finite baryon density using Polyakov loop correlators and presents lattice results for $N_f=2+1$ QCD with physical quark masses.

Findings

Screening masses increase with baryon chemical potential.

Static quark free energy decreases as baryon chemical potential increases.

Behavior of screening masses is analyzed at specific imaginary chemical potentials.

Abstract

We discuss the extension of gauge-invariant electric and magnetic screening masses in the Quark-Gluon Plasma to the case of a finite baryon density, defining them in terms of a matrix of Polyakov loop correlators. We present lattice results for $N_f=2+1$ QCD with physical quark masses, obtained using the imaginary chemical potential approach, which indicate that the screening masses increase as a function of $\mu_B$. A separate analysis is carried out for the theoretically interesting case $\mu_B/T=3 i \pi$, where charge conjugation is not explicitly broken and the usual definition of the screening masses can be used for temperatures below the Roberge-Weiss transition. Finally, we investigate the dependence of the static quark free energy on the baryon chemical potential, showing that it is a decreasing function of $\mu_B$ which displays a peculiar behavior as the pseudocritical transition temperature at $\mu_B=0$ is approached.