Three-loop matching of the vector current
  We evaluate the three-loop corrections to the matching coefficient of the vector current between Quantum Chromodynamics (QCD) and non-relativistic QCD. The result is presented in the MSbar scheme where large perturbative corrections are observed. The implications on the threshold production of top quark pairs are briefly discussed. 
Peter Marquard, Jan H. Piclum, Dirk Seidel and Matthias Steinhauser
hep-ph