Mass of the B_c Meson in Three-Flavor Lattice QCD
  We use lattice QCD to predict the mass of the $B_c$ meson. We use the MILC Collaboration's ensembles of lattice gauge fields, which have a quark sea with two flavors much lighter than a third. Our final result is $m_{B_c}=6304\pm12^{+18}_{- 0} MeV$. The first error bar is a sum in quadrature of statistical and systematic uncertainties, and the second is an estimate of heavy-quark discretization effects. 
Ian F. Allison, Christine T.H. Davies, Alan Gray, Andreas S. Kronfeld,   Paul B. Mackenzie, James N. Simone