The effect of sea quarks on the mass of the charm quark from Lattice QCD
  We compute the mass of the charm quark using both quenched and dynamical lattice QCD calculations. We examine the effects of mass dependent lattice artifacts by comparing two different formalisms for the heavy quarks. We take the continuum limit of the charm mass in quenched QCD by extrapolating from three different lattice spacings. At a fixed lattice spacing, the mass of the charm quark is compared between quenched QCD and dynamical QCD with a sea quark mass around strange. In the continuum limit of quenched QCD, we find m_c(m_c)=1.29(7)(13) GeV. No evidence was seen for unquenching. 
A. Dougall, C. M. Maynard and C. McNeile