B-meson decay constants: a more complete picture from full lattice QCD

TL;DR

This paper provides the first comprehensive lattice QCD calculations of B-meson decay constants for both pseudoscalar and vector mesons, including B*, B*_s, and B*_c, with detailed analysis of their ratios and dependencies.

Contribution

It introduces full lattice QCD results for vector B-meson decay constants, extending previous work limited to pseudoscalar mesons, and analyzes their ratios and quark mass dependence.

Findings

Ratios of vector to pseudoscalar decay constants are less than 1.0 for B and B_s mesons.

The ratio increases with the mass of the lighter quark.

Results agree with other HISQ formalism calculations for heavy quarks.

Abstract

We extend the picture of $B$-meson decay constants obtained in lattice QCD beyond those of the $B$, $B_s$ and $B_c$ to give the first full lattice QCD results for the $B^*$, $B^*_s$ and $B^*_c$. We use improved NonRelativistic QCD for the valence $b$ quark and the Highly Improved Staggered Quark (HISQ) action for the lighter quarks on gluon field configurations that include the effect of $u/d$, $s$ and $c$ quarks in the sea with $u/d$ quark masses going down to physical values. For the ratio of vector to pseudoscalar decay constants, we find $f_{B^*}/f_B$ = 0.941(26), $f_{B^*_s}/f_{B_s}$ = 0.953(23) (both $2\sigma$ less than 1.0) and $f_{B^*_c}/f_{B_c}$ = 0.988(27). Taking correlated uncertainties into account we see clear indications that the ratio increases as the mass of the lighter quark increases. We compare our results to those using the HISQ formalism for all quarks and find good agreement both on decay constant values when the heaviest quark is a $b$ and on the dependence on the mass of the heaviest quark in the region of the $b$. Finally, we give an overview plot of decay constants for gold-plated mesons, the most complete picture of these hadronic parameters to date.