The $D_s$,$D$, $B_s$ and $B$ decay constants from 2+1 flavor lattice QCD

Abstract

We present a study of the D and B leptonic decay constants on the MILC N f = 2 + 1 asqtad gauge ensembles using asqtad-improved staggered light quarks and clover heavy quarks in the Fermilab interpretation. Our previous analysis [1] computed the decay constants at lattice spacings a ≈ 0.14, 0.11 and 0.083 fm. We have extended the simulations to finer a ≈ 0.058 and 0.043 fm lattice spacings, and have also increased statistics; this allows us to address many important sources of uncertainty. Technical advances include a two-step two-point fit procedure, better tuning of the heavy quark masses and a better determination of the axial-vector current matching. The present analysis remains blinded, so here we focus on the improvements and their predicted impact on the error budget compared to the prior analysis.