Search for the Rare Decays B --> Kl^+l^- and B --> K^*l^+l^-

Abstract

We present results from a search for the flavor-changing neutral current decays $B\to K{\ell }^{+}{\ell }^{-}$ and $B\to K^{\ast }{\ell }^{+}{\ell }^{-}$, where ${\ell }^{+}{\ell }^{-}$ is either an $e^{+}{e}^{-}$ or ${\mu }^{+}{\mu }^{-}$ pair. The data sample comprises $22.7\times 10^6$ ${\rm Y}(4S)\to B\bar{B}$ decays collected with the BABAR detector at the PEP-II $B$ Factory. We obtain the 90% C.L. upper limits $\mathcal{B}(B\to K{\ell }^{+}{\ell }^{-})<0.50\times 10^{-6}$ and $\mathcal{B}(B\to K^{\ast }{\ell }^{+}{\ell }^{-})<2.9\times 10^{-6}$, close to Standard Model predictions for these branching fractions. We have also obtained limits on the lepton-family-violating decays $B\to K{e}^{\pm }{\mu }^{\mp }$ and $B\to K^{\ast }{e}^{\pm }{\mu }^{\mp }$.

7 pages, 3 figures, submitted to Physical Review Letters