Precise determination of the CKM matrix element $left| V_{cb}right|$ with $bar B^0 to D^{*,+} , ell^- , bar u_ell$ decays with hadronic tagging at Belle

The precise determination of the CKM matrix element $left| V_{cb}right|$ is important for carrying out tests of the flavour sector of the Standard Model. In this article we present a preliminary analysis of the $bar B^0 to D^{*,+} , ell^- , bar u_ell$ decay mode and its charge conjugate, selected in events that contain a fully reconstructed $B$-meson, using 772 million $e^+ , e^- to Upsilon(4S) to B bar B$ events recorded by the Belle detector at KEKB. Unfolded differential decay rates of four kinematic variables fully describing the $bar B^0 to D^{*,+} , ell^- , bar u_ell$ decay in the $B$-meson rest frame are presented. We measure the total branching fraction $mathcal{B}( bar B^0 to D^{*,+} , ell^- , bar u_ell ) = left(4.95 pm 0.11 pm 0.22 right) times 10^{-2}$, where the errors are statistical and systematic respectively. The value of $left|V_{cb} right|$ is determined to be $left( 37.4 pm 1.3 right) times 10^{-3}$. Both results are in good agreement with current world averages.