A precise determination of the charm quark's mass in quenched QCD

We present a lattice determination of the charm quark's mass, using the mass of the D_s meson as experimental input. All errors are under control with the exception of the quenched approximation. Setting the scale with F_K=160 MeV, our final result for the renormalization group invariant (RGI) quark mass is M_c = 1.654(45) GeV, which translates to m_c(m_c) =1.301(34) GeV for the running mass in the MSbar scheme. A 6 percent increase of the RGI quark mass is observed when the scale is set by the nucleon mass. This is a typical quenched scale ambiguity, which is reduced to about 3 percent for m_c(m_c), and to 4 percent for the mass ratio M_c/M_s. In contrast, the mass splitting m(Dstar_s)-m(D_s) changes from 117(11) MeV to 94(11) MeV, which is significantly smaller than the experimental value of 144 MeV.