The B and B_s Meson Decay Constants from Lattice QCD

TL;DR

This paper provides a highly precise lattice QCD calculation of B and B_s meson decay constants, improving accuracy over previous results through advanced computational techniques and updated lattice ensembles.

Contribution

It introduces an improved lattice QCD determination of B and B_s decay constants using HISQ and NRQCD quarks, achieving the most precise f_B value to date.

Findings

f_B = 0.191(9) GeV

f_{B_s} = 0.228(10) GeV

f_{B_s}/f_B = 1.188(18)

Abstract

We present a new determination of the B and B_s meson decay constants using NRQCD b-quarks, HISQ light and strange valence quarks and the MILC collaboration N_f=2+1 lattices. The new calculations improve on HPQCD's 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_{B_s} = 0.228(10)GeV and f_{B_s}/f_B = 1.188(18). Combining the new value for f_{B_s}/f_B with a recent very precise determination of the B_s meson decay constant based on HISQ b-quarks, f_{B_s} = 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.