$b \to s \ell^+ \ell^-$ 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 $B \to K^* \ell^+ \ell^-$ 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 $B \to K^* \ell^+ \ell^-$ decays is sensitive to possible non-standard sources of CP violation mediated by flavor changing neutral current $Z$-penguins.