Speaker
Description
We present recent progress in lattice calculations of semileptonic decays $B_{(s)} \to D_{(s)}\ell\nu$ form factors using the Oktay-Kronfeld (OK) action for the charm and bottom quarks. Data on four MILC HISQ ensembles: a12m310, a12m220, a09m310, a09m220 has been generated using the coherent sequential source to increase the statistics cost effectively. The excited states are controlled with multi-state fits to the 4 (or 6) source-sink separations. We will present the form factor for $B_{(s)} \to D_{(s)}^\ast\ell\nu$ at zero recoil, and the form factors for $B_{(s)} \to D_{(s)}\ell\nu$ at nonzero recoil. Current renormalization is underway using the nonperturbative RI-(S)MOM method. Results for the spectrum, decay constants and details of tuning the quark masses will be presented in a companion proceeding.
