  We study the heavy-quark momentum diffusion coefficient in far from
equilibrium gluon plasma in a self-similar regime using real-time lattice
techniques. We use 3 methods for the extraction: an unequal time electric field
2-point correlator integrated over the time difference, a spectral
reconstruction (SR) method based on the measured equal time electric field
correlator and a kinetic theory (KT) formula. The time-evolution of the
momentum diffusion coefficient extracted using all methods is consistent with
an approximate $t^{\frac{-1}{2}}$ power law. We also study the extracted
diffusion coefficient as a function of the upper limit of the time integration
and observe that including the infrared enhancement of the equal-time
correlation function in the SR calculation improves the agreement with the data
for transient time behavior considerably. This is a gauge invariant
confirmation of the infrared enhancement previously observed only in gauge
fixed correlation functions.
