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

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 ${\mu }_B/T=3i\pi$, 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.

Comments: 11 pages, 3 tables, 10 figures