Dependence of the static quark free energy on μB and the crossover temperature of Nf=2+1 QCD

We study the dependence of the static quark free energy on the baryon chemical potential for N-f = 2 + 1 QCD with physical quark masses, in a range of temperature spanning from 120 MeV up to 1 GeV and adopting a stout staggered discretization with two different values of the Euclidean temporal extension, N-t = 6 and N-t = 8. In order to deal with the sign problem, we exploit both Taylor expansion and analytic continuation, obtaining consistent results. We show that the dependence of the free energy on mu(B) is sensitive to the location of the chiral crossover, in particular the mu(B) susceptibility, i.e., the linear term in mu(2)(B) in the Taylor expansion of the free energy, has a peak around 150 MeV. We also discuss the behavior expected in the high temperature regime based on perturbation theory, and obtain a good quantitative agreement with numerical results.