Collinear and soft resummation in the large-x limit

I discuss general unified formulas for resumming collinear and soft contributions to QCD hard scattering cross sections at large x. Expansions of the resummed cross sections to next-to-next-to-next-to-leading order are also shown along with applications of the formalism.Comment: 4 pages, presented at DPF 2004, Riverside, California, August 26-31, 200

Crossed Threshold Resummation

We show that certain general properties of threshold and joint resummations in Drell-Yan cross sections hold as well for their crossed analogs in semi-inclusive deep-inelastic scattering and double-inclusive leptonic annihilation. We show that all plus-distribution corrections near threshold show the same structure, and are determined to all logarithmic order by two anomalous dimensions, one of which is a generalization of the D-term previously derived in Drell-Yan. We also discuss the possibility of universality in power corrections implied by the resummation.Comment: 8 page

Infrared finite coupling in Sudakov resummation: the precise set-up

I show that Sudakov resummation takes a transparent form if one deals with the second logarithmic derivative of the short distance coefficient functions for deep inelastic scattering and the Drell-Yan process. A uniquely defined Sudakov exponent emerges, and the constant terms not included in the exponent are conjectured to be given by the second logarithmic derivative of the massless quark form factor. The precise framework for the implementation of the dispersive approach to power corrections is set-up, yielding results in agreement with infrared renormalon expectations, but which are not tied to the single (dressed) gluon exchange approximation. Indications for a Banks-Zaks type of perturbative fixed point in the Sudakov effective coupling at low N_f are pointed out. Existence of a fixed point in the Sudakov coupling is argued to imply its universality.Comment: 5 pages, improved version of hep-ph/0606033, new result on universality of power corrections; version 2: added material, comments and references (to appear in Physical Review D (Rapid Communication)); version 3: a few misprints corrected, one reference added (journal version

Electroweak vector boson production in joint resummation

We study the application of the joint resummation to electroweak boson production at hadron colliders. The joint resummation formalism resums both threshold and transverse momentum corrections to the transverse momentum distribution at next-to-leading logarithmic accuracy. We obtain a good description of the transverse momentum distribution of Z bosons produced at the Tevatron collider.Comment: 5 pages, 2 figures. Talk presented by A. Kulesza at the XXXVIIth Rencontres de Moriond `QCD and high energy hadronic interactions', Les Arcs, Franc

The resummed Higgs boson transverse momentum distribution at the LHC

We apply QCD resummation techniques to study the transverse momentum distribution of Higgs bosons produced via gluon-gluon fusion at the LHC. In particular we focus on the joint resummation formalism which resums both threshold and transverse momentum corrections simultaneously. A comparison of results obtained in the joint and the standard recoil resummation frameworks is presented.Comment: 9 pages, 1 figure, uses appolb.cls. Contribution to the Proceedings of XXVII International Conference of Theoretical Physics, Ustron, Poland, September 15-21, 2003. To appear in Acta Physica Polonica

Threshold Resummation for Top-Pair Hadroproduction to Next-to-Next-to-Leading Log

We derive the threshold-resummed total cross section for heavy quark production in hadronic collisions accurate to next-to-next-to-leading logarithm, employing recent advances on soft anomalous dimension matrices for massive pair production in the relevant kinematic limit. We also derive the relation between heavy quark threshold resummations for fixed pair kinematics and the inclusive cross section. As a check of our results, we have verified that they reproduce all poles of the color-averaged q\bar{q} -> t\bar{t} amplitudes at two loops, noting that the latter are insensitive to the color-antisymmetric terms of the soft anomalous dimension.Comment: 18 pages; Expanded discussion, added references. Results unchanged

Factorization of e+e- Event Shape Distributions with Hadronic Final States in Soft Collinear Effective Theory

We present a new analysis of two-jet event shape distributions in soft collinear effective theory. Extending previous results, we observe that a large class of such distributions can be expressed in terms of vacuum matrix elements of operators in the effective theory. We match these matrix elements to the full theory in the two-jet limit without assuming factorization of the complete set of hadronic final states into independent sums over partonic collinear and soft states. We also briefly discuss the relationship of this approach to diagrammatic factorization in the full theory.Comment: 21 pages. Journal version. Defined an explicit thrust axis operator; clarified meaning of a delta function operato