Exclusive Decays of Charm and Beauty

Exclusive decays of B and D mesons are discussed with the focus on the theoretical problem how to calculate the relevant hadronic matrix elements of weak operators in the framework of QCD sum rules. The three lectures are devoted to 1. leptonic decays and decay constants 2. semileptonic decays and form factors 3. nonleptonic decays and nonfactorizable amplitudes. I shall introduce some of the basic concepts, describe various calculational techniques, and illustrate the numerical results. The latter are compared with lattice and quark model predictions and, where possible, with experimental data. Applications include the determination of V_{ub} from B -> \pi \bar{l} \nu_l and B -> \rho \bar{l} \nu_l, and an estimate of the phenomenological coefficient a_2 for B -> J/\psi K.Comment: 51 pages, 21 figures, 4 tables, Latex, uses eqnumber.sty Lectures at the International Summer School of Physics "Enrico Fermi", Course CXXXVII, Varenna, Italy, 1997, version to be published in the proceeding

LEP Constraints on 5-Dimensional Extensions of the Standard Model

We study minimal 5-dimensional extensions of the Standard Model, in which all or only some of the SU(2)$_L$ and U(1)$_Y$ gauge fields and Higgs bosons propagate in the fifth compact dimension. In all the 5-dimensional settings, the fermions are assumed to be localized on a 3-brane. In addition, we present the consistent procedure for quantizing 5-dimensional models in the generalized $R_\xi$ gauge. Bounds on the compactification scale between 4 and 6 TeV, depending on the model, are established by analyzing electroweak precision measurements and LEP2 cross sections.Comment: 6 pages, talk given at the 10th international conference on ``Supersymmetry and Unification of Fundamental Interactions,'' Hamburg, Germany, 17--23 June 200

QCD Sum Rules for Heavy Flavors

We give a short review of QCD sum rule results for B and D mesons and Lambda_Q and Sigma_Q baryons. We focus mainly on recent developments concerning semileptonic B->pion and D->pion transitions, pion couplings to heavy hadrons, decay constants and estimates of the b quark mass from a baryonic sum rule, and the extraction of the pion distribution amplitude from CLEO data.Comment: 12 pages, LaTeX, Talk given by O.Yakovlev at the 4th Workshop on Continuous Advances in QCD, Minneapolis, May 12-14, 2000; to appear in the Proceeding