Heavy quark diffusion in perturbative QCD at next-to-leading order

We compute the momentum diffusion coefficient of a heavy quark in a hot QCD plasma, to next-to-leading order in the weak-coupling expansion. Corrections arise at O(g(s)); physically they represent interference between overlapping scatterings, as well as soft, electric scale (p similar to gT) gauge field physics, which we treat using the hard thermal loop effective theory. In 3-color, 3-flavor QCD, the momentum diffusion constant of a fundamental representation heavy quark at next-to-leading order is kappa = 16 pi/3 alpha T-2(s)3(ln/1g(s) + 0.07428+1.9026g(s)). The convergence of the perturbative expansion is poor.