Application of fixed scale approach to static quark free energies in quenched and 2+1 flavor lattice QCD with improved Wilson quark action

摘要

Free energies between static quarks and Debye screening masses in thequark-gluon plasma are studied on the basis of Polyakov-line correlations inlattice simulations of 2+1 flavors QCD with the renormalization-group improvedgluon action and the $O(a)$-improved Wilson quark action. We performsimulations at $m_{\rm PS}/m_{\rm V} = 0.63$ (0.74) for light (strange) flavorswith lattice sizes of $32^3 \times N_t$ with $N_t=4$--12. We adopt thefixed-scale approach, where temperature can be varied without changing thespatial volume and renormalization factor. We find that, at short distance, thefree energies of static quarks in color-singlet channel converge to thestatic-quark potential evaluated from the Wilson-loop at zero-temperature, inaccordance with the expected insensitivity of short distance physics to thetemperature. At long distance, the free energies of static quarks approach totwice the single-quark free energies, implying that the interaction betweenstatic quarks is fully screened. The screening properties can be well describedby the screened Coulomb form with appropriate Casimir factor at hightemperature. We also discuss a limitation of the fixed-scale approach at hightemperature.