We present a new determination of the Bs leptonic decay constant from lattice QCD simulations that use gluon configurations from MILC and a highly improved discretization of the relativistic quark action for both valence quarks. Our result, fBs=0.225(4)\,GeV, is almost three times more accurate than previous determinations. We analyze the dependence of the decay constant on the heavy quark's mass and obtain the first empirical evidence for the leading 1/mh dependence predicted by Heavy Quark Effective Theory (HQET). As a check, we use our analysis technique to calculate the mBs−mηb/2 mass difference. Our result agrees with experiment to within errors of 11MeV (better than 2%). We discuss how to extend our analysis to other quantities in Bs and B physics, making 2%-precision possible for the first time.
@article{arxiv.1110.4510,
title = {High-Precision $f_{B_s}$ and HQET from Relativistic Lattice QCD},
author = {C. McNeile and C. T. H. Davies and E. Follana and K. Hornbostel and G. P. Lepage},
journal= {arXiv preprint arXiv:1110.4510},
year = {2015}
}