Precision $B_c$ and $B_s$ mass calculations
  We give improved results for B meson masses using NRQCD $b$ quarks and HISQ light valence quarks for a range of lattice spacings and sea quark masses enabling controlled extrapolation to the physical point. 
E. B. Gregory, C. T. H. Davies, K. Y. Wong, E. Follana, E. Gamiz, G.   P. Lepage, J. Shigemitsu