Semileptonic B → D ( ∗ ) ` ν Decay Form Factors using the Oktay-Kronfeld Action

We report recent progress in calculating semileptonic form factors for the B̄→ D∗`ν̄ and B̄→ D`ν̄ decays using the Oktay-Kronfeld (OK) action for bottom and charm quarks. We use the second order in heavy quark effective power counting O(λ 2) improved currents in this work. The HISQ action is used for the light spectator quarks. We analyzed four 2+1+1-flavor MILC HISQ ensembles with a ≈ 0.09fm, 0.12fm and Mπ ≈ 220MeV, 310MeV: a09m220, a09m310, a12m220, a12m310. Preliminary results for B→ D∗`ν decays form factor hA1(w) at zero recoil (w= 1) are reported. Preliminary results for B→D`ν decays form factors h±(w) over a kinematic range 1 < w < 1.3 are reported as well.