B Meson Decay Constants Using Relativistic Heavy Quarks

We present an update on ongoing work to extract pseudoscalar and vector decay constants for $B^{(\ast )}$, $B_s^{(\ast )}$ and $B_c^{(\ast )}$ mesons and determine phenomenologically-interesting ratios such as $f_{B_s}\mathrm{/}{f}_B$ or $f_{B^{\ast }}\mathrm{/}{f}_B$. Our calculation is based on ${\mathrm{N}}_{\mathrm{f}}=2+1$ dynamical flavour gauge field ensembles generated by the RBC/UKQCD collaborations using domain-wall fermions and the Iwasaki gauge action. Using domain-wall light, strange, and charm quarks and relativistic $b$ quarks, we obtain results at multiple lattice spacings and valence quark masses.