Transport coefficients from in-medium quarkonium dynamics

Abstract

The in-medium dynamics of heavy particles are governed by transport coefficients. The heavy quark momentum diffusion coefficient, kappa, is an object of special interest in the literature, but one which has proven notoriously difficult to estimate, despite the fact that it has been computed by weak-coupling methods at next-to-leading order accuracy, and by lattice simulations of the pure SU(3) gauge theory. Another coefficient, gamma, has been recently identified. It can be understood as the dispersive counterpart of kappa. Little is known about gamma. Both kappa and gamma arc, however, of foremost importance in heavy quarkonium physics as they entirely determine the in and out of equilibrium dynamics of quarkonium in a medium, if the evolution of the density matrix is Markovian, and the motion, quantum Brownian; the medium could be a strongly or weakly coupled plasma. In this paper, using the relation between kappa, gamma and the quarkonium in-medium width and mass shift respectively, we evaluate the two coefficients from existing 2 + 1 flavor lattice QCD data. The resulting range for kappa is consistent with earlier determinations, the one for gamma is the first nonperturbative determination of this quantity.