Instanton-induced production of QCD jets

We consider the instanton contributions for the production of a gluon jet with large transverse momentum in QCD. We find that Mueller's corrections corresponding to the rescattering of hard quanta are likely to remove contributions of large instantons, making this cross section well defined. This observation generalizes the previous discussion of instanton effects in the deep inelastic scattering and suggests that all hard processes in the QCD receive hard non-perturbative corrections from instantons of small size, of order $\rho\sim 1/(Q\alpha_s)$.Comment: LATEX, 7 pages, DESY 94-17

NLO evolution of color dipoles

The small-$x$ deep inelastic scattering in the saturation region is governed by the non-linear evolution of Wilson-line operators. In the leading logarithmic approximation it is given by the BK equation for the evolution of color dipoles. In the next-to-leading order the BK equation gets contributions from quark and gluon loops as well as from the tree gluon diagrams with quadratic and cubic nonlinearities. We calculate the gluon contribution to small-x evolution of Wilson lines (the quark part was obtained earlier).Comment: 43 pages, 12 figure

Gluon Distributions and Color Charge Correlations in a Saturated Light-cone Wavefunction

We describe the light-cone wavefunction in the saturation regime in terms of the density of gluons per unit of transverse phase space, the occupation number, and in terms of the color charge correlator. The simple McLerran- Venugopalan model gives what are claimed to be general results for the phase space gluon density, but it does not well describe the general case for the charge correlator. We derive the general momentum dependence and rapidity dependence of the color charge correlator which exhibits strong color shielding. A simplel physical picture which leads to these general results is described.Comment: 17 pages, Latex, 7 figure

Gluon TMD in particle production from low to moderate x

We study the rapidity evolution of gluon transverse momentum dependent distributions appearing in processes of particle production and show how this evolution changes from small to moderate Bjorken x.Comment: 36 pages, 3 figures. arXiv admin note: text overlap with arXiv:1505.0215

Rapidity evolution of gluon TMD from low to moderate x

We study how the rapidity evolution of gluon transverse momentum dependent distribution changes from nonlinear evolution at small $x \ll 1$ to linear evolution at moderate $x \sim 1$.Comment: 70 pages, 7 figures, published versio

Scattering of color dipoles: from low to high energies

A dipole-dipole scattering amplitude is calculated exactly in the first two orders of perturbation theory. This amplitude is an analytic function of the relative energy and the dipoles' sizes. The cross section of the dipole-dipole scattering approaches the high-energy BFKL asymptotics starting from a relatively large rapidity $\sim 5$.Comment: 13 pages, 10 postscript figures, typos correcte

Photon impact factor in the next-to-leading order

An analytic coordinate-space expression for the next-to-leading order photon impact factor for small-$x$ deep inelastic scattering is calculated using the operator expansion in Wilson lines.Comment: 5 pages, 3 figure

Factorization and Effective Action for High-Energy Scattering in QCD

I demonstrate that the amplitude of the high-energy scattering can be factorized in a convolution of the contributions due to fast and slow fields. The fast and slow fields interact by means of Wilson-line operators -- infinite gauge factors ordered along the straight line. The resulting factorization formula gives a starting point for a new approach to the effective action for high-energy scattering.Comment: Talk presented at the workshop "Continuous Advances in QCD", (Minneapolis), April 1998. 15 pages, 3 eps figures, Latex using sprocl.sty and psfig.te

Power corrections to TMD factorization for Z-boson production

A typical factorization formula for production of a particle with a small transverse momentum in hadron-hadron collisions is given by a convolution of two leading-twist TMD parton densities with cross section of production of the final particle by the two partons. For practical applications at a given transverse momentum, though, one should estimate at what momenta the power corrections to TMD factorization formula due to higher-twist operators become essential. In this paper we calculate the first power corrections to TMD factorization formula for Z-boson production and Drell-Yan process in high-energy hadron-hadron collisions. At the leading order in $N_c$ power corrections are expressed in terms of leading-twist TMDs by QCD equations of motion.Comment: 44 pages, 3 figures. v2: text changes. arXiv admin note: text overlap with arXiv:1706.0141

Photon impact factor and kTk_T-factorization for DIS in the next-to-leading order

The photon impact factor for the BFKL pomeron is calculated in the next-to-leading order (NLO) approximation using the operator expansion in Wilson lines. The result is represented as a NLO $k_T$-factorization formula for the structure functions of small-$x$ deep inelastic scattering.Comment: 13 pages, 4 figures, typos corrected. arXiv admin note: substantial text overlap with arXiv:1009.472