Rare decays $B\to X_s{l}^{+}{l}^{-}$ and $B\to K^{(\ast )}{l}^{+}{l}^{-}$ in SM and beyond

Abstract

After a brief review of the inclusive and exclusive rare semileptonic decays of B mesons in the standard model (SM), an overview of recent theoretical developments in this field is given. New physics effects on various observables such as branching ratio, backward-forward asymmetry, polarization of lepton and CP violation in the decays are anlyzed in models beyond SM (supersymmetric models and two Higgs doublet models).

Comments: 6 pages, invited talk given at the Fourth International Conference on Hyperons, Charm and Beauty Hadrons, June 27-30, 2000, Valencia, Spain, to appear in the Proceedings of the Conference, typo corrected