We study the electric conductivity of hot QCD matter at various temperatures T within the off-shell parton-hadron-string dynamics transport approach for interacting partonic, hadronic or mixed systems in a finite box with periodic boundary conditions. The response of the strongly interacting system in equilibrium to an external electric field defines the electric conductivity σ(0). We find a sizable temperature dependence of the ratio σ(0)/T well in line with calculations in a relaxation time approach for T(c)

We study the kinetic and chemical equilibration in "infinite" parton matter within the partonhadron-string dynamics off-shell transport approach, which is based on a dynamical quasiparticle model (DQPM) for partons matched to reproduce lattice QCD results-including the partonic equation of state-in thermodynamic equilibrium. The "infinite" parton matter is simulated by a system of quarks and gluons within a cubic box with periodic boundary conditions, at various energy densities, initialized out of kinetic and chemical equilibrium. We investigate the approach of the system to equilibrium and the time scales for the equilibration of different observables. We, furthermore, study particle distributions in the strongly interacting quark-gluon plasma (sQGP) including partonic spectral functions, momentum distributions, abundances of the different parton species, and their fluctuations (scaled variance, skewness, and kurtosis) in equilibrium. We also compare the results of the microscopic calculations with the ansatz of the DQPM. It is found that the results of the transport calculations are in equilibrium well matched by the DQPM for quarks and antiquarks, while the gluon spectral function shows a slightly different shape due to the mass dependence of the gluon width generated by the explicit interactions of partons. The time scales for the relaxation of fluctuation observables are found to be shorter than those for the average values. Furthermore, in the local subsystem, a strong change of the fluctuation observables with the size of the local volume is observed. These fluctuations no longer correspond to those of the full system and are reduced to Poissonian distributions when the volume of the local subsystem becomes small.

Measurements of inclusive spectra and mean multiplicities of π ± , K ± , p andp produced in inelastic p + p interactions at incident projectile momenta of 20,31,40, 80 and 158 GeV/c ( √ s = 6.3, 7.7, 8.8, 12.3 and 17.3 GeV, respectively) were performed at the CERN Super Proton Synchrotron using the large acceptance NA61/SHINE hadron spectrometer. Spectra are presented as function of rapidity and transverse momentum and are compared to predictions of current models. The measurements serve as the baseline in the NA61/SHINE study of the properties of the onset of deconfinement and search for the critical point of strongly interacting matter.

Dilepton production in In+In collisions at 158 A·GeV is studied within the microscopic partonhadron-string dynamics (PHSD) transport approach that incorporates explicit partonic degrees-offreedom, dynamical hadronization as well as the more familiar hadronic dynamics in the final reaction stages. A comparison to the data of the NA60 Collaboration shows that the measured dilepton yield is well described by including the collisional broadening of vector mesons, while simultaneously accounting for the electromagnetic radiation of the strongly coupled quark-gluon plasma (sQGP) via off-shell quark-antiquark annihilation, quark annihilation with additional gluon Bremsstrahlung and the gluon-Compton scattering mechanisms. In particular, the spectra in the intermediate mass range (1 GeV ≤ M ≤ 2.5 GeV) are dominated by quark-antiquark annihilation in the nonperturbative QGP. Also, the observed softening of the transverse mass spectra at intermediate masses (1 GeV ≤ M ≤ 2.5 GeV) is approximately reproduced. Furthermore, for dileptons of low masses (M < 0.6 GeV), we find a sizeable contribution from the quark annihilation with additional gluon bremsstrahlung, thus providing another possible window for probing the properties of the sQGP.PACS numbers: 25.75.Cj, 25.75.Nq, 24.85.+p,

We study the shear and bulk viscosities of partonic and hadronic matter as functions of temperature T within the parton-hadron-string dynamics (PHSD) off-shell transport approach. Dynamical hadronic and partonic systems in equilibrium are studied by the PHSD simulations in a finite box with periodic boundary conditions. The ratio of the shear viscosity to entropy density η(T )/s(T ) from PHSD shows a minimum (with a value of about 0.1) close to the critical temperature Tc, while it approaches the perturbative QCD limit at higher temperatures in line with lattice QCD (lQCD) results. For T < Tc, i.e., in the hadronic phase, the ratio η/s rises fast with decreasing temperature due to a strong decrease of the entropy density s in the hadronic phase at decreasing T . Within statistics, we obtain practically the same results in the Kubo formalism and in the relaxation time approximation. The bulk viscosity ζ(T )-evaluated in the relaxation time approach-is found to strongly depend on the effects of mean fields (or potentials) in the partonic phase. We find a significant rise of the ratio ζ(T )/s(T ) in the vicinity of the critical temperature Tc, when consistently including the scalar mean-field from PHSD, which is also in agreement with that from lQCD calculations. Furthermore, we present the results for the ratio (η + 3ζ/4)/s, which is found to depend nontrivially on temperature and to generally agree with the lQCD calculations as well. Within the PHSD calculations, the strong maximum of ζ(T )/η(T ) close to Tc has to be attributed to mean-field (or potential) effects that in PHSD are encoded in the temperature dependence of the quasiparticle masses, which is related to the infrared enhancement of the resummed (effective) coupling g(T ).