B and B-s meson decay constants from lattice QCD

We present a new determination of the B and B-s meson decay constants using nonrelativistic quantum chromodynamics (NRQCD) b-quarks, highly improved staggered quark (HISQ) light and strange valence quarks and the MILC collaboration N-f = 2 + 1 lattices. The new calculations improve on HPQCD\u27s earlier work with NRQCD b-quarks by replacing AsqTad with HISQ valence quarks, by including a more chiral MILC fine ensemble in the analysis, and by employing better tuned quark masses and overall scale. We find f (B) = 0.191(9) GeV, f (Bs) = 0.228(10) GeV and f (Bs)/f (B) = 1.188(18). Combining the new value for f (Bs)/f (B) with a recent very precise determination of the B-s meson decay constant based on HISQ b-quarks, f (Bs) = 0.225(4) GeV, leads to f (B) = 0.189(4) GeV. With errors of just 2.1% this represents the most precise f (B) available today