11th International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions

We compute the heavy quark momentum diffusion coefficient using effective kinetic theory for a system going through bottom-up isotropization until approximate hydrodynamization. We find that when matching the nonthermal diffusion coefficient to the thermal one for the same energy density, the observed deviations throughout the whole evolution are withing 30% from the thermal value. When matching for other quantities we observe considerably larger deviations. We also observe that the diffusion coefficient in the transverse direction dominates at large occupation number, whereas for an underoccupied system the longitudinal diffusion coefficient dominates. While the ratio of the diffusion coefficients does not follow the usual hydrodynamical attractor, we observe the emergence of a limiting weak coupling attractor governed by bottom-up scaling.