One-loop lattice artifacts of a dynamical charm quark
  For a few observables in O(a) improved lattice QCD, we compute discretization effects arising from the vacuum polarization of a heavy quark at one-loop order. In particular, the force between static quarks, the running coupling in the Schrodinger functional and a related quantity, {\bar \upsilon}, are considered. Results show that the cutoff effects of a dynamical charm quark are typically smaller than those present in the pure gauge theory. This perturbative result is a good indication that dynamical charm quarks are feasible already now. 
Andreas Athenodorou and Rainer Sommer
hep-lat