NLL Corrections for B-Meson Radiative Exclusive Decays

We calculate the next-to-leading corrections to the branching ratio of exclusive $B\to K^* \gamma$ decay. The renormalization scale dependence is reduced compared to the leading logarithmic result but there remains a dependence on a cutoff parameter of the hadronic model. The calculated corrections increase the predicted branching ratio by about 10%, but it remains in agreement with the experimental value.Comment: 16 pages, 8 figure

Photon Energy Spectrum in B→XsγB \to X_s \gamma and Comparison with Data

A comparison of the inclusive photon energy spectrum in the radiative decay \BGAMAXS, measured recently by the CLEO collaboration, with the standard model is presented, using a $B$-meson wave function model and improving earlier perturbative QCD-based computations of the same. The dependence of the photon energy spectrum on the non-perturbative model parameters, $p_F$, the $b$-quark Fermi momentum in the $B$ hadron, and $m_q$, the spectator quark mass, is explicitly shown, allowing a comparison of these parameters with the ones obtained from the analysis of the lepton energy spectrum in semileptonic $B$ decays. Taking into account present uncertainties, we estimate \BBGAMAXS = (2.55 \pm 1.28) \times 10^{-4} in the standard model, assuming \absvts/\absvcb= 1.0. Comparing this with the CLEO measurement \BBGAMAXS = (2.32 \pm 0.67) \times 10^{-4} implies \absvts/\absvcb= 1.1 \pm 0.43, in agreement with the CKM unitarity.Comment: 16 pages (including 5 Figures as encapsulated ps-files: use epsf and rotate

Package for Calculations and Simplifications of Expressions with Dirac Matrixes (MatrixExp)

This paper describes a package for calculations of expressions with Dirac matrixes. Advantages to existing similar packages are described. MatrixExp package is intended for simplification of complex expressions involving $\gamma$-matrixes, providing such tools as automatic Feynman parameterization, integration in $d$-dimensional space, sorting and grouping of results in a given order. Also, in comparison with existing similar package Tracer, presented package MatrixExp has more enhanced input possibility. User-available functions of MatrixExp package are described in detail. Also an example of calculation of Feynman diagram for process $b\to s\gamma g$ with application of functions of MatrixExp package is presented

Tree-level contribution to \bar{B} -> X_d gamma using fragmentation functions

We evaluate the most important tree-level contributions connected with the b-> u \bar{u} d gamma transition to the inclusive radiative decay \bar{B}-> X_d gamma using fragmentation functions. In this framework the singularities arising from collinear photon emission from the light quarks (u, \bar{u} and d) can be absorbed into the (bare) quark-to-photon fragmentation function. We use as input the fragmentation function extracted by the ALEPH group from the two-jet cross section measured at LEP, where one of the jets is required to contain a photon. To get the quark-to-photon fragmentation function at the fragmentation scale \mu_F \sim m_b, we use the evolution equation, which we solve numerically. We then calculate the (integrated) photon energy spectrum for b-> u \bar{u} d gamma related to the operators P^u_{1,2}. For comparison, we also give the corresponding results when using nonzero (constituent) masses for the light quarks.Comment: 13 pages, 4 figure

Indirect search for supersymmetry in rare B decays

QCD corrections to the gluino induced contribution to b --> s gamma are shown to be important in order to extract reliable bounds on the off-diagonal elements of the squark mass matrices.Comment: 4 pages including 2 postscript figure

Exclusive Radiative Decays of B Mesons

We present within the Standard Model the exclusive radiative decays B -> K*/rho gamma and B_(s/d) -> gamma gamma in QCD factorization based on the heavy-quark limit m_b >> Lambda_QCD. For the decays with a vector meson in the final state we give results complete to next-to-leading order in QCD.Comment: 4 pages, contributed to QCD 02: High-Energy Physics International Conference in Quantum Chromodynamics, Montpellier, France, 2-9 July 200