Exploring the partonic phase at finite chemical potential within an extended off-shell transport approach

We extend the parton-hadron-string dynamics (PHSD) transport approach in the partonic sector by explicitly calculating the total and differential partonic scattering cross sections as a function of temperature T and baryon chemical potential mu(B) on the basis of the effective propagators and couplings from the dynamical quasiparticle model (DQPM) that is matched to reproduce the equation of state of the partonic system above the deconfinement temperature T-c from lattice quantum chromodynamics (QCD). We calculate the collisional widths for the partonic degrees of freedom at finite T and mu(B) in the time-like sector and conclude that the quasiparticle limit holds sufficiently well. Furthermore, the ratio of shear viscosity eta over entropy density s, that is, eta/s, is evaluated using the collisional widths and compared to lattice QCD(lQCD) calculations for mu(B) = 0 as well. We find that the ratio eta/s does not differ very much from that calculated within the original DQPM on the basis of the Kubo formalism. Furthermore, there is only a very modest change of eta/s with the baryon chemical mu(B) as a function of the scaled temperature T/T-c(mu(B)). This also holds for a variety of hadronic observables from central A + A collisions in the energy range 5 GeV <= sNN <= 200 GeV when implementing the differential cross sections into the PHSD approach. Accordingly, it will be difficult to extract finite mu(B) signals from the partonic dynamics based on "bulk" observables.