Studies of B and B_s Meson Leptonic Decays with NRQCD Bottom and HISQ   Light/Strange Quarks
  We present a progress report on new calculations of B and B_s meson decay constants employing NRQCD heavy and HISQ light valence quarks and using MILC N_f = 2+1 AsqTad lattices. Bare quark masses have been retuned in accord with HPQCD's new r_1 scale. We find significant reductions in discretization effects compared to previous calculations with AsqTad light valence quarks. Matching of the NRQCD/HISQ heavy-light axial vector current is carried out at one-loop order including all relevant dimension 4 current corrections. 
Junko Shigemitsu, Heechang Na, Christine Davies, Ron Horgan, Chris   Monahan, and Peter Lepage
hep-lat hep-ph