We give a progress report on a project aimed at a high-precision calculation of the decay constants fB and fBs from simulations with HISQ heavy and light valence and sea quarks. Calculations are carried out with several heavy valence-quark masses on ensembles with 2+1+1 flavors of HISQ sea quarks at five lattice spacings and several light sea-quark mass ratios mud/ms, including approximately physical sea-quark masses. This range of parameters provides excellent control of the continuum limit and of heavy-quark discretization errors. We present a preliminary error budget with projected uncertainties of 2.2~MeV and 1.5~MeV for fB and fBs, respectively.
@article{arxiv.1511.02294,
title = {Decay constants $f_B$ and $f_{B_s}$ from HISQ simulations},
author = {Fermilab Lattice and MILC Collaborations and : and A. Bazavov and C. Bernard and C. Bouchard and N. Brown and C. DeTar and D. Du and A. X. El-Khadra and E. D. Freeland and E. Gámiz and Steven Gottlieb and U. M. Heller and J. Komijani and A. S. Kronfeld and J. Laiho and L. Levkova and P. B. Mackenzie and C. Monahan and T. Primer and Heechang Na and E. T. Neil and J. N. Simone and R. L. Sugar and D. Toussaint and R. S. Van de Water and R. Zhou},
journal= {arXiv preprint arXiv:1511.02294},
year = {2015}
}