With the aim of clarification of color correlations among quarks, we investigate the color correlation between a static quark and an antiquark (static q q ˉ ) below and above the phase transition temperature T c through the entanglement entropy (EE). By a quenched lattice QCD calculation on an anisotropic lattice adopting the standard Wilson gauge action in the Coulomb gauge, we compute a reduced density matrix ρ defined in the color space and the entanglement entropy S EE constructed from ρ . The spatial volume is L 3 = 2 4 3 , and the temporal extents are N T = 12 , 13, 14, 15, 16, 18, 20 and 24, with a gauge coupling β = 5.75 and a renormalized anisotropy ξ = 4.0 , which corresponds to temperatures between 180 and 370?MeV. From an analysis of ρ and S EE , the color correlation between q q ˉ pairs is obtained as a function of the interquark distance R and the temperature T . Below T c , the R -dependence of the color correlation resembles that at T = 0 : the quark’s color correlation gradually decreases as R increases due to the color screening by in-between gluons. Above T c , due to the deconfinement phase transition, the color correlation among quarks is found to quickly disappear. Further, we investigate the color screening effect via the screening mass defined by ρ and discuss the differences in the screening properties between the small and large R regions.
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