Update on $B\to D^{\ast }\ell \nu$ form factor at zero-recoil using the Oktay-Kronfeld action

Abstract

We present an update on the calculation of $\bar{B}\to D^{\ast }\ell \bar{\nu }$ semileptonic form factor at zero recoil using the Oktay-Kronfeld bottom and charm quarks on $N_f=2+1+1$ flavor HISQ ensembles generated by the MILC collaboration. Preliminary results are given for two ensembles with $a\approx 0.12$ and $0.09$ fm and $M_{\pi }\approx 310$ MeV. Calculations have been done with a number of valence quark masses, and the dependence of the form factor on them is investigated on the $a\approx 0.12$ fm ensemble. The excited state is controlled by using multistate fits to the three-point correlators measured at 4--6 source-sink separations.

Comments: 7 pages and 4 figures. Talk at The 36th Annual International Symposium on Lattice Field Theory - LATTICE2018