We describe gluon-pair production from a space-time dependent chromofield via vacuum polarization within the framework of the background field method of QCD. The processes we consider are first order in the action. We derive the corresponding source terms for gluon pair production for situations that can be described by a 1+1 dimensional approach. Especially, we observe that within the range of...

Renormalization of twist-three operators and integrable lattice models. Abstract We address the problem of solution of the QCD three-particle evolution equations which govern the Q 2-dependence of the chiral-even quark-gluon-quark and three-gluon correlators contributing to a number of asymmetries at leading order and the transversely polarized structure function g 2 (x Bj). The quark-gluon-qua...

In exclusive J/ψ production by polarized photons incident on polarized protons , a finite polarization asymmetry arises because of c¯ c Fermi-motion and binding-energy effects. The asymmetry depends on the polarized nonfor-ward gluon distribution of the proton and thus gives information on gluon polarization in the proton. The analyzing power, however, is rather small. Gluon polarization in the...

We construct the effective Hamiltonian which governs the renormalization group flow of the gluon distribution with increasing energy and in the leading logarithmic approximation. This Hamiltonian defines a two–dimensional field theory which involves two types of Wilson lines: longitudinal Wilson lines which describe gluon recombination (or merging) and temporal Wilson lines which account for gl...

We present a calculation of diffractive charm jet production at hadron colliders in perturbative QCD based on the two-gluon exchange model. Differing from the previous calculations, we abandon the use of the effective color-singlet vitual gluon simplification, and use the real gluon in the calculations for the partonic process. We find the final result is free of the linear singularities due to...

The computation of exclusive QCD jet observables at higher orders requires a method for the subtraction of infrared singular configurations arising from multiple radiation of real partons. One commonly used method at next-to-leading order (NLO) is based on the antenna factorization of colour-ordered matrix elements, and uses antenna functions to subtract the real radiation singularities. Up to ...

The enhanced suppression of J/ψ production at large xF in pA collisions is studied in the framework of gluon depletion at large x1. The nonperturbative process that modifies the gluon distribution as the gluons propagate in nuclear matter is described by an evolution equation with a kernal to be determined by phenomenology. With nuclear shadowing and anti-shadowing taken into account, the effec...

The anomalous dimensions of the gluon and ghost fields as well as those of the ghost-ghost-gluon and quark-quark-gluon vertexes are analytically computed at four loops in pQCD. Taken together with already available anomalous dimensions of the coupling constant, the quark field and the mass the results lead to complete knowledge of all renormalization constant entering into the renormalization o...

We calculate the transverse momentum dependence of the medium-induced gluon energy distribution radiated off massive quarks in spatially extended QCD matter. In the absence of a medium, the distribution shows a characteristic mass-dependent depletion of the gluon radiation for angles u,m/E , the so-called dead cone effect. Medium modifications of this spectrum are calculated as a function of qu...

We summarize our recent results on the resummation of hard-scattering coefficient functions and on-shell form factors in massless perturbative QCD. The threshold resummation has been extended to the fourth logarithmic order for deep-inelastic scattering, Drell-Yan lepton pair production and Higgs production via gluon-gluon fusion. The leading six infrared pole terms have been derived to all ord...