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

Event-Based Transverse Momentum Resummation

We have developed a framework for automated transverse momentum resummation for arbitrary electroweak final states based on reweighting tree-level events. It is fully differential in the kinematics of the electroweak final states, which facilitates a straightforward analysis of arbitrary observables in the small transverse momentum region. We have implemented the resummation at next-to-next-to-leading logarithmic accuracy and match to next-to-leading fixed-order results using the event generator MadGraph5_aMC@NLO. Results for $Z$ and $W$ boson production with leptonic decay as well as $WZ$ production are presented. We compare to experimental measurements for the transverse momentum and the angular observable $\phi^*$.Comment: 28 pages, 13 figures. v2: journal versio

Infrared singularities of QCD amplitudes with massive partons

A formula for the two-loop infrared singularities of dimensionally regularized QCD scattering amplitudes with an arbitrary number of massive and massless legs is derived. The singularities are obtained from the solution of a renormalization-group equation, and factorization constraints on the relevant anomalous-dimension matrix are analyzed. The simplicity of the structure of the matrix relevant for massless partons does not carry over to the case with massive legs, where starting at two-loop order new color and momentum structures arise, which are not of the color-dipole form. The resulting two-loop three-parton correlations can be expressed in terms of two functions, for which some general properties are derived. This explains observations recently made by Mitov et al. in terms of symmetry arguments.Comment: 7 pages, 1 figure; v2: minor changes, reference added; v3: note added, correcting some statements regarding F1 and f2 in light of the recent calculations in [45,46], references update

NNLL Resummation for Jet Broadening

The resummation for the event-shape variable jet broadening is extended to next-to-next-to-leading logarithmic accuracy by computing the relevant jet and soft functions at one-loop order and the collinear anomaly to two-loop accuracy. The anomaly coefficient is extracted from the soft function and expressed in terms of polylogarithmic as well as elliptic functions. With our results, the uncertainty on jet-broadening distributions is reduced significantly, which should allow for a precise determination of the strong coupling constant from the existing experimental data and provide a consistency check on the extraction of alpha_s from higher-log resummations of thrust.Comment: 44 pages, 9 figure