T -matrix approach to quarkonium correlation functions in the quark-gluon plasma

We study the evolution of heavy quarkonium states with temperature in a quark-gluon plasma (QGP) by evaluating the in-medium Q-Q̄ T-matrix within a reduced Bethe-Salpeter equation in both S- and P-wave channels. The underlying interaction kernel is extracted from recent finite-temperature QCD lattice calculations of the singlet free energy of a Q-Q̄ pair. The bound states are found to gradually move above the Q-Q̄ threshold after which they rapidly dissolve in the hot system. The T-matrix approach is particularly suited to investigate these mechanisms as it provides a unified treatment of bound and scattering states including threshold effects and the transition to the (perturbative) continuum. We apply the T-matrix to calculate Q-Q̄ spectral functions as well as pertinent Euclidean-time correlation functions which are compared to results from lattice QCD. A detailed analysis reveals large sensitivities to the interplay of bound and scattering states, to temperature-dependent threshold energies, and to the reconstructed correlator used for normalization. We furthermore investigate the impact of finite-width effects on the single-quark propagators in the QGP as estimated from recent applications of heavy-quark rescattering to RHIC data.