We propose a model-independent method to determine the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element ‖${\mathit{V}}_{\mathit{ub}}$‖ from exclusive B and D decays. Combining information obtainable from B→ρlν${\mathrm{¯}}_{\mathcal{l}}$, B→${\mathit{K}}^{\mathrm{*}}$νν¯, D→ρl¯${\nu }_{\mathcal{l}}$, and D→${\mathit{K}}^{\mathrm{*}}$l¯${\nu }_{\mathcal{l}}$, a determination of ‖${\mathit{V}}_{\mathit{ub}}$‖ is possible, with an uncertainty from theory of around 10%. Theoretical uncertainties in the B→${\mathit{K}}^{\mathrm{*}}$ll¯ decay rate are discussed. © 1996 The American Physical Society.

• Received 7 December 1995

DOI:https://doi.org/10.1103/PhysRevD.53.4937