  We present an NLO analysis of the massive vector current correlator at
temperatures above a few hundred MeV. The physics of this correlator originates
from a transport peak, related to heavy quark diffusion, and from the
quark-antiquark threshold, related to quarkonium physics. In the bottom case
both can be studied with separate effective theories, but for charm these may
not be accurate, so a study within the full theory is needed. Working in
imaginary time, the NLO correlator can be computed in unresummed perturbation
theory; comparing with lattice data, we find good agreement. Subsequently we
inspect how non-perturbative modifications of the transport peak would affect
the imaginary-time correlator. The massive NLO quark-number susceptibility is
also contrasted with numerical measurement.
