$b\to s{\ell }^{+}{\ell }^{-}$ decays in and beyond the Standard Model

Abstract

We briefly review the status of rare radiative and semileptonic $b\to s(\gamma ,{\ell }^{+}{\ell }^{-})$, ($\ell =e,\mu$) decays. We discuss possible signatures of new physics in these modes and emphazise the role of the exclusive channels. In particular, measurements of the Forward-Backward asymmetry in $B\to K^{\ast }{\ell }^{+}{\ell }^{-}$ decays and its zero provide a clean test of the Standard Model, complementary to studies in $b\to s\gamma$ decays. Further, the Forward-Backward CP asymmetry in $B\to K^{\ast }{\ell }^{+}{\ell }^{-}$ decays is sensitive to possible non-standard sources of CP violation mediated by flavor changing neutral current $Z$-penguins.

Comments: Invited Talk at 7th Conference on the Intersections of Particle and Nuclear Physics, Quebec City, Quebec, Canada, May 22-28, 2000