$|V_{cb}|$ from the ${\bar{B}}^0\to D^{\ast +}{\ell }^{-}\bar{\nu }$ zero-recoil form factor using $2+1+1$ flavour HISQ and NRQCD

Abstract

We present the status of our ongoing calculation of the zero-recoil form factor for the semileptonic decay ${\bar{B}}^0\to D^{\ast +}{l}^{-}\bar{\nu }$ using lattice QCD with 2+1+1 flavours of highly improved staggered quarks in the sea (the MILC HISQ configurations) and using non-relativistic QCD for the bottom quark. We combine our result for $F(1)$ with the latest HFAG average of ${\eta }_{EW}F(1)|V_{cb}|$ to get a preliminary value for $|V_{cb}|$.

Contribution to the Proceedings of the 34th annual International Symposium on Lattice Field Theory, 24-30 July 2016, University of Southampton, UK. 6 pages, 1 figure