Semileptonic $B\to D^{(\ast )}\ell \nu$ Decay Form Factors using the Oktay-Kronfeld Action

Abstract

We report recent progress in calculating semileptonic form factors for the $\bar{B}\to D^{\ast }\ell \bar{\nu }$ and $\bar{B}\to D\ell \bar{\nu }$ decays using the Oktay-Kronfeld (OK) action for bottom and charm quarks. We use the second order in heavy quark effective power counting $\mathcal{O}({\lambda }^2)$ 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 $a\approx 0.09\mathrm{fm}$, $0.12\mathrm{fm}$ and $M_{\pi }\approx 220\mathrm{MeV}$, $310\mathrm{MeV}$: $a09m220$, $a09m310$, $a12m220$, $a12m310$. Preliminary results for $B\to D^{\ast }\ell \nu$ decays form factor $h_{A_1}(w)$ at zero recoil ($w=1$) are reported. Preliminary results for $B\to D\ell \nu$ decays form factors $h_{\pm }(w)$ over a kinematic range $1<w<1.3$ are reported as well.

Comments: 7 pages, 7 figures, Lattice 2019 proceeding