Heavy-quark free energy, Debye mass, and spatial string tension at finite temperature in two flavor lattice QCD with Wilson quark action

We study Polyakov loop correlations and spatial Wilson loop at finite temperature in two-flavor QCD simulations with the RG-improved gluon action and the clover-improved Wilson quark action on a 16{sup 3}x4 lattice. From the line of constant physics at m{sub PS}/m{sub V}=0.65 and 0.80, we extract the heavy-quark free energies, the effective running coupling g{sub eff}(T) and the Debye screening mass m{sub D}(T) for various color channels of heavy quark-quark and quark-antiquark pairs above the critical temperature. The free energies are well approximated by the screened Coulomb form with the appropriate Casimir factors at high temperature. The magnitude and the temperature dependence of the Debye mass are compared to those of the next-to-leading-order thermal perturbation theory and to a phenomenological formula in terms of g{sub eff}(T). We make a comparison between our results with the Wilson quark action and the previous results with the staggered quark action. The spatial string tension is also studied in the high temperature phase and is compared to the next-to-next-leading-order prediction in an effective theory with dimensional reduction.