A heavy quark–antiquark pair in hot QCD

Thermodynamics of a heavy quark–antiquark pair in SU(3)-QCD is studied both below and above the deconfinement critical temperature Tc. In the quenched case, a model of the string passing through heavy valence gluons yields a correct estimate of Tc and the critical behavior of the string tension below Tc. For two light flavors, entropy and internal energy below Tc can be obtained from the partition function of heavy–light mesons and baryons. To calculate the free energy of the system above Tc, we apply second-order perturbation theory in the interaction of the quark–gluon plasma constituents with the static quark–antiquark pair. The results for the entropy and internal energy, obtained both below and above Tc, are compared with recent lattice data.