$|V_{ub}|$ from exclusive $B$ and $D$ decays

Abstract

We propose a model-independent method to determine the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{ub}|$ from exclusive $B$ and $D$ decays. Combining information obtainable from $B\to \rho \ell {\bar{\nu }}_{\ell }$, $B\to K^{\ast }\nu \bar{\nu }$, $D\to \rho \bar{\ell }{\nu }_{\ell }$ and $D\to K^{\ast }\bar{\ell }{\nu }_{\ell }$, a determination of $|V_{ub}|$ is possible, with an uncertainty from theory of around 10\%. Theoretical uncertainties in the $B\to K^{\ast }\ell \bar{\ell }$ decay rate are discussed.

Comments: 20 pages revtex, 6 figures included using epsf