Nikolaos Kidonakis

Two-loop soft anomalous dimensions for single top quark associated production with a W- or H-

I present results for the two-loop soft anomalous dimensions for associated production of a single top quark with a W boson or a charged Higgs boson. The calculation uses expressions for the massive cusp anomalous dimension, which are presented in different forms, and it allows soft-gluon resummation at next-to-next-to-leading-logarithm (NNLL) accuracy. From the NNLL resummed cross section I derive approximate NNLO cross sections for bg{yields}tW{sup -} and bg{yields}tH{sup -} at LHC energies of 7, 10, and 14 TeV.

Next-to-next-to-leading-order collinear and soft gluon corrections for t-channel single top quark production

I present the resummation of collinear and soft-gluon corrections to single top quark production in the t channel at next-to-next-to-leading logarithm accuracy using two-loop soft anomalous dimensions. The expansion of the resummed cross section yields approximate next-to-next-to-leading-order cross sections. Numerical results for t-channel single top quark (or single antitop) production at the Tevatron and the LHC are presented, including the dependence of the cross sections on the top quark mass and the uncertainties from scale variation and parton distributions. Combined results for all single top quark production channels are also given.

Next-to-next-to-leading soft-gluon corrections for the top quark cross section and transverse momentum distribution

I present results for top quark production in hadronic collisions at LHC and Tevatron energies. The soft-gluon corrections to the differential cross section are resummed at nextto-next-to-leading-logarithm (NNLL) accuracy via the two-loop soft anomalous dimension matrices. Approximate next-to-next-to-leading-order (NNLO) differential and total cross

RESUMMATION FOR QCD HARD SCATTERING

Abstract We resum distributions that are singular at partonic threshold (the elastic limit) in heavy quark production, in terms of logarithmic behavior in moment space. The method may be applied to a variety of cross sections sensitive to the edge of phase space, including transverse momentum distributions. Beyond leading logarithm, dependence on the moment variable is controlled by a matrix renormalization group equation, reflecting the evolution of composite operators that represent the color structure of the underlying hard scattering. At next-to-leading logarithmic accuracy, these evolution equations may be diagonalized, and moment dependence in the cross section is a sum of exponentials. Beyond next-to-leading logarithm, resummation involves matrix-ordering. We give a detailed analysis for the case of heavy quark production by light quark annihilation and gluon fusion.

Theoretical top quark cross section at the Fermilab Tevatron and the CERN LHC

We present results for the top quark pair cross section at the Tevatron and the LHC. We use the resummed double differential cross section, employing the fully kinematics-dependent soft-anomalous-dimension matrices, to calculate the soft-gluon contributions at next-to-next-to-leading order (NNLO). We improve and update our previous estimates by refining our methods, including further subleading terms, and employing the most recent parton distribution function sets. The NNLO soft corrections significantly enhance the NLO cross section while considerably reducing the scale dependence. We provide a detailed discussion of all theoretical uncertainties in our calculation, including kinematics, scale, and parton distribution uncertainties, and clarify the differences between our work and other approaches in the literature.

Evolution of color exchange in QCD hard scattering

Abstract In QCD hard scattering cross sections, the color content of the underlying hard scattering evolves with a factorization scale. This evolution is controlled by an anomalous dimension matrix, specific to each hard-scattering reaction. Anomalous dimensions are determined from the renormalization of products of ordered exponentials of the gauge field, which describe the coherent radiation of gluons by incoming hadrons and the observed jets or particles of the final state. The anomalous dimensions depend on the kinematics of the underlying hard scattering, but are free of collinear singularities. A number of these matrices are available in the literature. Here, we exhibit one-loop mixing matrices for the full list of 2 → 2 reactions involving light quarks and gluons. The eight-by-eight anomalous dimension matrix for gluon-gluon scattering shows a simplified structure in the basis corresponding to definite color exchange in the t -channel.

Next-to-next-to-leading order soft gluon corrections in top quark hadroproduction.

We calculate next-to-next-to-leading order soft-gluon corrections to top quark total and differential cross sections in hadron colliders. We increase the accuracy of our previous estimates by including additional subleading terms, including next-to-next-to-next-to-leading-logarithmic and some virtual terms. We show that the kinematics dependence of the cross section vanishes near threshold and is reduced away from it. The factorization and renormalization scale dependence of the cross section is also greatly reduced. We present results for the top quark total cross sections and transverse momentum distributions at the Fermilab Tevatron and the CERN LHC.

Single Top Quark Production at the Fermilab Tevatron: Threshold Resummation and Finite-order Soft Gluon Corrections

I present a calculation of threshold soft-gluon corrections to single top-quark production in pp collisions via all partonic processes in the t and s channels and via associated top quark and W boson production. The soft-gluon corrections are formally resummed to all orders, and finite-order expansions of the resummed cross section are calculated through next-to-next-to-next-to-leading-order (NNNLO) at next-to-leading logarithmic (NLL) accuracy. Numerical results for single top-quark production at the Tevatron are presented, including the dependence of the cross sections on the top-quark mass and on the factorization and renormalization scales. The threshold corrections in the t channel are small while in the s channel they are large and dominant. Associated tW production remains relatively minor due to the small leading-order cross section even though the K factors are large.

Two-Loop Soft Anomalous Dimensions and Next-to-Next-to-Leading-Logarithm Resummation for Heavy Quark Production

I present results for two-loop soft anomalous dimensions for heavy quark production which control soft-gluon resummation at next-to-next-to-leading-logarithm accuracy. I derive an explicit expression for the exact result and study it numerically for top quark production via e(+)e(-)-->tt, and I construct a surprisingly simple but very accurate approximation. I show that the two-loop soft anomalous dimensions with massive quarks display a simple proportionality relation to the one-loop result only in the limit of vanishing quark mass. I also discuss the extension of the calculation to single top and top pair production in hadron colliders.

Effects of higher order threshold corrections in high E(T) jet production

Results for higher-order threshold enhancements in high-