B-decays in the heavy-quark expansion

Progress in the theoretical description of B-meson decays, in particular decays to light hadrons, is reviewed. The factorization properties of such decays can be analyzed using the soft-collinear effective theory. Applications of the effective theory to both inclusive and exclusive decays are discussed.Comment: Talk presented at the 15th Topical Conference on Hadron Collider Physics (Michigan State University, June 2004) and at the 11th International QCD Conference (Montpellier, July 2004). 14 pages, 4 figure

Lorentz Invariant Baryon CHPT

Using the example of the elastic $\pi N$-amplitude, we discuss the low energy expansion of QCD amplitudes in the sector with baryon number one. We show that the chiral expansion of these amplitudes breaks down in certain regions of phase space and present a framework which leads to a coherent description throughout the low energy region, while keeping Lorentz and chiral invariance manifest at every stage of the calculation. We explain how to construct a representation of the pion nucleon scattering amplitude in terms of functions of a single variable, which is valid to $O(q^4)$ and properly accounts for the $\pi\pi$- and $\pi N$-cuts required by unitarity.Comment: Latex, 12 pages. Plenary talk given at "Chiral Dynamics 2000: Theory and Experiment", Newport News, USA, 17-22 July 200

Factorization and Resummation for Jet Broadening

Jet broadening is an event-shape variable probing the transverse momenta of particles inside jets. It has been measured precisely in e+e- annihilations and is used to extract the strong coupling constant. The factorization of the associated cross section at small values of the broadening is afflicted by a collinear anomaly. Based on an analysis of this anomaly, we present the first all-order expressions for jet-broadening distributions, which are free of large perturbative logarithms in the two-jet limit. Our formulae reproduce known results at next-to-leading logarithmic order but also extend to higher orders.Comment: 15 pages, 4 figure