Theory of radiative B decays

Theory of charmless radiative B decays is reviewed. Existence of uncontrolled non-perturbative effects in the inclusive rate at O(alpha_s) is reminded.Comment: Talk at the 3rd International Conference on B Physics and CP Violation, Taipei, December 3-7, 1999. 10 pages, including figures, uses graphic

Weak Radiative Decays of the B Meson and Bounds on MH±M_{H^\pm} in the Two-Higgs-Doublet Model

In a recent publication [6], the Belle collaboration updated their analysis of the inclusive weak radiative B-meson decay, including the full dataset of (772 +_ 11) x 10^6 BBbar pairs. Their result for the branching ratio is now below the Standard Model prediction [7,8], though it remains consistent with it. However, bounds on the charged Higgs boson mass in the Two-Higgs-Doublet Model get affected in a significant manner. In the so-called Model-II, the 95% C.L. lower bound on $M_{H^\pm}$ is now in the 570-800 GeV range, depending quite sensitively on the method applied for its determination. Our present note is devoted to presenting and discussing the updated bounds, as well as to clarifying several ambiguities that one might encounter in evaluating them. One of such ambiguities stems from the photon energy cutoff choice, which deserves re-consideration in view of the improved experimental accuracy.Comment: 15 pages, 4 figure

NNLO QCD counterterm contributions to BB \to XsγX_s \gamma for the physical value of mcm_c

One of the most important O($\alpha_s^2$) corrections to the $B \to X_s \gamma$ branching ratio originates from interference of contributions from the current-current and photonic dipole operators. Its value has been estimated using an interpolation in the charm quark mass between the known results at $m_c=0$ and for $m_c \ll m_b/2$. An explicit calculation for the physical value of $m_c$ is necessary to remove the associated uncertainty. In the present work, we evaluate all the ultraviolet counterterm contributions that are relevant for this purpose.Comment: journal version, references added; 14 pages, 3 figures, 1 table; some intermediate results in ancillary file

Determining the sign of the b -> s gamma amplitude

The latest Belle and BaBar measurements of the inclusive B -> X_s l^+ l^- branching ratio have smaller errors and lower central values than the previous ones. We point out that these results indicate that the sign of the b -> s gamma amplitude is the same as in the SM. This underscores the importance of B -> X_s l^+ l^- in searches for new physics, and may be relevant for neutralino dark matter analyses within the MSSM.Comment: Journal version, references added, minor modifications. 4 pages, 2 figure

Anomalous Wtb coupling effects in the weak radiative B-meson decay

We study the effect of anomalous Wtb couplings on the B -> Xs gamma branching ratio. The considered couplings are introduced as parts of gauge-invariant dimension-six operators that are built out of the Standard Model fields only. One-loop contributions from the charged-current vertices are assumed to be of the same order as the tree-level flavour-changing neutral current ones. Bounds on the corresponding Wilson coefficients are derived.Comment: 5 pages, 2 figures. The arXiv version remains extended w.r.t. the journal version. The first function in Eq. (12) has been corrected in v3, implying slight changes in the numerical results. Conclusions remain unaffecte