Weak Decays of Heavy-Quark Systems

The recent theoretical progress in the description of semileptonic decays in the framework of the heavy mass expansion is summarized. Both inclusive and exclusive decays are considered.Comment: Contribution to the XXIXth Rencontres de Moriond (Electroweak Interactions and Unified Theories}, Meribel, France, March 12-19, 1994, LaTeX, 10 pages, two figues appended after \end{document} as uu-encoded and compressed .eps files, uses epsf., CERN-TH.7264/9

Subleading Light-cone distributions functions in the decays Lambda(b) --> X(s) Gamma and Lambda(b) --> X(u) Lepton Anti-Nu

In this paper we investigate the subleading twist corrections to the photon energy spectrum in the decay Lambda_b -> X_s \gamma and to the lepton energy spectrum in Lambda_b -> X_u l \bar{\nu}. As a first step we rederive the matching coefficients of the subleading twist using a much simpler method. Parametrizing the matrix elements for Lambda_b and using reparametrization invariance, we show that the energy spectra close to the endpoints are given in terms of only a single universal function.Comment: LATEX,The complete paper is also available via the www at http://www-ttp.physik.uni-karlsruhe.de/Preprints/ . Discussion section improve

Light-Quark Decays in Heavy Hadrons

We consider weak decays of heavy hadrons (bottom and charmed) where the heavy quark acts as a spectator. Theses decays are heavily phase-space suppressed but may become experimentally accessible in the near future. These decays are interesting as a QCD laboratory to study the behaviour of the light quarks in the colour-background field of the heavy spectator.Comment: 11 pages, 6 table

Hadronic Spectrum in Inclusive Semileptonic B Decays

We evaluate the inclusive semileptonic B decay spectrum as a function of the final-state hadrons energy to second order in the inverse quark mass expansion and tree level in $\alpha_{s}$. We argue that there is an energy interval below the $c$ production threshold that could be used to determine $V_{ub}$.Comment: 10 pages, UCLA/94/TEP/10. (LaTeX file, one uuencoded PostScript figure appended at the end.

Direct CP Violation In Radiative B Decays

We discuss the role of the radiative B decays $B \to X_{s/d} \gamma$ in our search for new physics focusing on the issue of direct CP violation. We discuss in some detail a SM prediction for the CP asymmetries in inclusive $b \to s/d$ transitions, namely $\mid \Delta {\cal B}(B \to X_s \gamma) + \Delta {\cal B}(B \to X_d \gamma) \mid \sim 1 \cdot 10^{-9}$. Any measured value in significant deviation of this estimate would indicate new sources of CP violation beyond the CKM phase.Comment: latex, 8 pages, 3 figure

Improved Estimates for the Parameters of the Heavy Quark Expansion

We give improved estimates for the non-perturbative parameters appearing in the heavy quark expansion for inclusive decays. While the parameters appearing in low orders of this expansion can be extracted from data, the number of parameters in higher orders proliferates strongly, making a determination of these parameters from data impossible. Thus, one has to rely on theoretical estimates which may be obtained from an insertion of intermediate states. In this paper we refine this method and attempt to estimate the uncertainties of this approach.Comment: 18 pages (v2: Fixed sign error in section 3. conclusions unchanged

The endpoint region in radiative quarkonia decays

We consider the inclusive radiative decays quarkonium -> gamma + hadrons and examine the effects of soft QCD radiation on the photon energy spectrum near the endpoint.Comment: Presented at the DPF2000 Meeting, Ohio State University, August 2000. (Version 2: minor typos corrected.