We compute NNLO (O(α2 s)) corrections to the hard-scattering kernels entering the QCD factorization formula for B → V γ decays, where V is a light vector meson. We give complete NNLO results for the dipole operators Q7 and Q8, and partial results for Q1 valid in the large-β0 limit and neglecting the NNLO correction from hard spectator scattering. Large perturbative logarithms in the hard-scatte...

We discuss corrections from the elastic limit (partonic threshold) in hadronic hard-scattering cross sections. We show why these corrections can be large at all orders in perturbation theory, and describe their resummation to arbitrary logarithmic accuracy. In particular, we discuss the role of color exchange in the hard scattering. This enables us to generalize the resummation of the Drell-Yan...

We present a new resummation formula for the Drell-Yan cross section. The formal resummation of threshold corrections in Drell-Yan hard-scattering functions produces an exponent with singularities from the infrared pole of the QCD running coupling. Our reformulation treats such ‘infrared renormalons’ by a principal value prescription, analogous to a modified Borel transform. The resulting expre...

“Static” structure functions are the probabilistic distributions computed from the square of the light-front wavefunctions of the target hadron. In contrast, the “dynamic” structure functions measured in deep inelastic lepton-hadron scattering include the effects of rescattering associated with the Wilson line. Initialand final-state rescattering, neglected in the parton model, can have a profo...

The scattering of two charged strongly interacting particles is described on the basis of the P -matrix approach. In the P matrix, it is proposed to isolate explicitly the background term corresponding to purely Coulomb interaction, whereby it becomes possible to improve convergence of the expansions used and to obtain a correct asymptotic behavior of observables at high energies. The expressio...

We discuss recent work on methods for incorporating nonleading QCD corrections in parton shower algorithms. Parton shower Monte Carlo event generators are the main practical tool to describe multi-particle final states in high energy collisions. These event generators couple a leading-order (LO) hard scattering to a showering, treated basically in the leading logarithm approximation. Many nonle...

Conventional jet algorithms are based on a deterministic view of the underlying hard scattering process. Each outgoing parton from the hard scattering is associated with a hard, well separated jet. This approach is very successful because it allows quantitative predictions using lowest order perturbation theory. However, beyond leading order in the coupling constant, when quantum fluctuations a...

As is well-known factorization is an important property of QCD whithout which we would not be able to calculate form factors or cross sections. Factorization into a hard parton-level subprocess to be calculated from perturbative QED and/or QCD, and soft hadronic matrix elements which are subject to non-perturbative QCD and are not calculable at present, has been shown to hold for a number of re...