Estimates of the Weak Annihilation Contributions to the Decays B→ρ+γB \to \rho + \gamma and B→ω+γB \to \omega + \gamma

The dominant long-distance contributions to the exclusive radiative decays $B \to \rho (\omega) + \gamma$ involve photon emission from the light quarks at large distances, which cannot be treated perturbatively. We point out that this emission can be described in a theoretically consistent way as the magnetic excitation of quarks in the QCD vacuum and estimate the corresponding parity-conserving and parity-violating amplitudes using the light-cone QCD sum rule approach. These are then combined with the corresponding short-distance contribution from the magnetic moment operator in the same approach, derived earlier, to estimate the decay rates $\Gamma (B \to \rho(\omega) + \gamma)$. The implications of this result for the determination of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements in radiative $B$ decays are worked out.Comment: 13 pages, Latex, 3 figures (not included) available on request from [email protected]

CP Violation and Flavour Mixing in the Standard Model -- 1996 Update

We review and update the constraints on the parameters of the quark flavour mixing matrix $V_{CKM}$ in the standard model and estimate the resulting CP asymmetries in $B$ decays, taking into account recent experimental and theoretical developments. With the updated CKM matrix we present the currently-allowed range of the ratios $|V_{td}/V_{ts}|$ and $|V_{td}/V_{ub}|$, as well as the standard model predictions for the \bsbsbar\ mixing parameter \xs (or, equivalently, \delms) and the quantities $\sin 2\alpha$, $\sin 2\beta$ and $\sin^2\gamma$, which characterize the CP-asymmetries in $B$-decays.Comment: 23 pages, LaTeX, 9 figures; updated to include latest experimental results on Bs-Bs(bar) mixin

Rare B Decays in the Standard Model

We discuss the electromagnetic-penguin-dominated radiative B decays $B \to X_s + \gamma, ~B^{\pm (0)} \to K^{*\pm (0)} + \gamma$, and $B_s \to \phi + \gamma$ in the context of the standard model (SM) and their Cabibbo-Kobayashi-Maskawa (CKM)-suppressed counterparts, $B \to X_d + \gamma$, $B^\pm \to \rho^\pm + \gamma, ~B^{0} \to (\rho^{0}, \omega) + \gamma$, and $B_s \to K^{* 0} + \gamma$, using QCD sum rules for the exclusive decays. The importance of these decays in determining the parameters of the CKM matrix is emphasized. The semileptonic decays $B \to X_s \ell^+ \ell^-$ are also discussed in the context of the SM and their role in determining the Wilson coefficients of the effective theory is stressed. Comparison with the existing measurements are made and SM-based predictions for a large number of rare B decays are presented.Comment: Latex2e, 25 pages, 4 figures (require epsf.sty, rotate). Invited talk. To be published in Proceedings of the 4th International Workshop 'Beauty-96', Roma, June 17 - 21, 199

Flavour Changing Neutral Current Processes in B Decays

We review the theory and experimental measurements in the flavour changing neutral current (FCNC) processes involving B decays in the context of the standard model (SM). The role of these processes in determining the weak mixing matrix elements is stressed.Comment: Latex2e, 16 pages, 4 figures (requires epsf.sty, espcrc2.sty) To be published in the Proceedings of the Fourth KEK Topical Conference on Flavour Physics, KEK, Tsukuba, Japan, October 29-31, 199