arXiv subjects

Yuri V. Kovchegov

Publications and source records attributed to Yuri V. Kovchegov.

113 records · Page 7Linked to original sources

arXiv1998

Gluon production in current-nucleus and nucleon-nucleus collisions in a quasi-classical approximation

We calculate gluon production in deep inelastic scattering of the current j= - (1/4) F_{μν}^a F_{μν}^a off a large nucleus and in nucleon-nucleus collisions. In a covariant gauge calculation the transverse momentum spectrum of the gluon is determined by the final state interactions of the gluon with the nucleons in the nucleus. In a light-cone gauge calculation final state interactions are absent and these effects come from the light-cone wavefunction of the nucleus. We work in an approximation which neglects QCD evolution of gluons in the nucleon, that is in a quasi-classical approximation.

hep-ph↗

arXiv1997

Unitarity Corrections and High Field Strengths in High Energy Hard Collisions

Unitarity corrections to the BFKL description of high energy hard scattering are viewed in large $N_c$ QCD in light-cone quantization. In a center of mass frame unitarity corrections to high energy hard scattering are manifestly perturbatively calculable and unrelated to questions of parton saturation. In a frame where one of the hadrons is initially at rest unitarity corrections are related to parton saturation effects and involve potential strengths $A_μ\sim 1/g.$ In such a frame we describe the high energy scattering in terms of the expectation value of a Wilson loop. The large potentials $A_μ\sim 1/g$ are shown to be pure gauge terms allowing perturbation theory to again describe unitarity corrections and parton saturation effects. Genuine nonperturbative effects only come in at energies well beyond those energies where unitarity constraints first become important.

hep-ph↗

arXiv1997

Classical Gluon Radiation in Ultrarelativistic Nucleus-Nucleus Collisions

The classical Yang-Mills equations are solved perturbatively in covariant gauge for a collision of two ultrarelativistic nuclei. The nuclei are taken as ensembles of classical color charges on eikonal trajectories. The classical gluon field is computed in coordinate space up to cubic order in the coupling constant g. We construct the Feynman diagrams corresponding to this field and show the equivalence of the classical and diagrammatic approaches. An argument is given which demonstrates that at higher orders in g the classical description of the process breaks down. As an application, we calculate the energy, number, and multiplicity distributions of produced soft gluons and reproduce earlier results by Gunion and Bertsch and by Kovner, McLerran, and Weigert.

hep-ph↗

arXiv1997

Quantum structure of the non-Abelian Weizsacker-Williams field for a very large nucleus

We consider the McLerran-Venugopalan model for calculation of the small-$x$ part of the gluon distribution function for a very large ultrarelativistic nucleus at weak coupling. We construct the Feynman diagrams which correspond to the classical Weizsäcker-Williams field found previously [Yu. V. Kovchegov, Phys. Rev. D 54, 5463 (1996)] as a solution of the classical equations of motion for the gluon field in the light-cone gauge. Analyzing these diagrams we obtain a limit for the McLerran-Venugopalan model. We show that as long as this limit is not violated a classical field can be used for calculation of scattering amplitudes.

hep-ph↗

arXiv1996

Non-Abelian Weizsacker-Williams field and a two-dimensional effective color charge density for a very large nucleus

We consider a very large ultra-relativistic nucleus. Assuming a simple model of the nucleus and weak coupling we find a classical solution for the gluon field of the nucleus and construct the two-dimensional color charge density for McLerran-Venugopalan model out of it. We prove that the density of states distribution, as a function of color charge density, is Gaussian, confirming the assumption made by McLerran and Venugopalan.

hep-ph↗