Rare B-meson decays

The Standard Model of strong, weak and electromagnetic interactions though enjoying enormous phenomenological success is clearly far from perfect. The Higgs sector seems arbitrary. The lepton and quark masses, the coupling constants, the angles and phases of the Cabbibo, Kobayashi, Maskawa (C.K.M.) mixing matrix, are all parameters which are not explained but are put into the model. Besides, the Standard Model has not been well tested beyond the tree level. The study of rare B-decays is peculiarly suited to clarify some of these aspects, as well as to probe for new physics beyond the Standard Model. Since the b-quark is quite heavy the spectator approximation can be used with more confidence than for K or D decays. The author studies the decays b → sl+l-, B → Kl+l- and B → K*l+l-, which involve b → s transitions at the one loop level with corrections from Q.C.D. effects. The dilepton mass spectrum depends on the unknown top mass and the C.K.M. parameters. The decays B → Kψ and B → K*ψ, which involve long distance effects where the open-quotes cclose quotes quark from the b → cW- pairs with the open-quotes bar cclose quotes from the W- → s bar c to form a bound charmonium state, are studied, and the results agree with experiment. These charmonium can decay into l+l- pairs complicating the study of the semileptonic decays mentioned above. The author also calculates several B-decays into charmless and strangeless hadronic models. The factorisation approximation is used. The form factors for all of the calculations are obtained from a constituent quark model. The author found many of the non-leptonic modes to have branching ratios of the order of magnitude of about 10-5. These modes should be accessible to experiments soon, as seen from the present experimental limits