Exclusive B --> M l^+ l^- (M=\pi, K, \rho, K^*) Decays and Determinations of |V_{ts}| (and |V_{td}/V_{ts}|)

Abstract

We examine the possibility for precise determination of |V_{ts}| (and |V_{td}/V_{ts}|) from the exclusive decays, $B-->K{\ell }^{+}{\ell }^{-},B-->K^{\ast }{\ell }^{+}{\ell }^{-}$ (and $B-->\pi {\ell }^{+}{\ell }^{-},B-->\rho {\ell }^{+}{\ell }^{-}$). We show that the ratio |V_{ts}| can be extracted experimentally with a small theoretical uncertainty from hadronic form--factors, if we {\bf appropriately constrain} kinematical regions of $q^2$. We also give detailed analytical and numerical results on the differential decay width $d\Gamma (B-->K^{\ast }{\ell }^{+}{\ell }^{-})/d{q}^2$, and the ratios of integrated branching fractions, $\mathcal{B}(B-->\rho {\ell }^{+}{\ell }^{-})/\mathcal{B}(B-->K^{\ast }{\ell }^{+}{\ell }^{-})$. We estimate that one can determine the ratio |V_{ts}| from those decays within theoretical accuracy of $\sim 10$.

Comments: 16 pages, 4 figures, shortened for PLB publication