arXiv subjects

Eugene Levin

Publications and source records attributed to Eugene Levin.

100 records · Page 6Linked to original sources

arXiv1998

The BFKL high energy asymptotics in the next-to-leading approximation

We discuss the high energy asymptotics in the next-to-leading (NLO) BFKL equation. We find a general solution for Green functions and consider two properties of the NLO BFKL kernel: running QCD coupling and large NLO corrections to the conformal part of the kernel. Both of these effects lead to Regge-BFKL asymptotics only in the limited range of energy ($y = \ln(s/q q_0) \leq (\as)^{- {5/3}}$) and change the energy behaviour of the amplitude for higher values of energy. We confirm the oscillation in the total cross section found in Ref. \cite{ROSS} in the NLO BFKL asymptotics, which shows that the NLO BFKL has a serious pathology.

hep-ph↗

arXiv1997

Where are the BFKL Pomeron and shadowing corrections in DIS?

In this talk, I will argue that the HERA experimental data show that the typical parameter ($κ$) responsible for the value of the shadowing corrections (SC) in DIS is so large that the BFKL Pomeron is hidden under SC. The SC turn out to be large enough but mostly for the gluon structure function which is not well determined by the available experimental data and by the current theoretical procedure.

hep-ph↗

arXiv1997

Lessons and puzzles of DIS at low x (high energy)

This talk is a rather sceptical review of our knowledge and understanding of deep inelastic scattering at low x (high energy). We show that the well known success of the DGLAP evolution equations in describing of experimental HERA data brought more problems and puzzles than answers. We advocate that more systematic theoretical and experimental investigations of the nonperturbative QCD are needed to clarify physics of DIS at high energy.

hep-ph↗

arXiv1997

In combat with nonperturbative QCD

This talk is the second part of the summary of the theory section at DIS'97. We demonstrated that theory of the "hard" processes, based on QCD, has achieved a better understanding of available experimental data during the past year. This was due to the remarkable success achieved in calculating of high order corrections in perturbative QCD (see the summary talk of S. Forte) as well as progress in nonpertutbative QCD approaches.

hep-ph↗

arXiv1997

A violation of the factorization theorem for "hard" inclusive production

This talk is a digest of Ref.[1](E.Gotsman,E. Levin and U. Maor: TAUP 2416/97, hep-ph/9705205,Phys. Lett. (in press)) where a new mechanism for hard inclusive production, which leads to a violation of the factorization theorem (FT), is suggested. Numericalestimates for the effect are given for high energy hadron (nucleus) scattering.

hep-ph↗

arXiv1996

Diffractive Leptoproduction of Small Masses in QCD

In this paper we consider the process of diffraction dissociation in deep inelastic scattering producing a small mass. This process is analyzed by the calculation of $\bar q\, q$ and $\bar q\, q\, G$ production. We show that the small distance contributions ($r_{\perp}\,\propto\,1/Q$) to the longitudinal polarised virtual photon dominate the diffractive channels. Formulae for the cross section using the gluon density are written within the framework of perturbative QCD. We show that the production of small masses by a transverse polarised photon is concentrated at moderate values of $r_{\perp} \,\sim\,1 GeV^{-1}$, where the pQCD approach is valid. It is shown that only $\bar q\, q$ pair production contributes to diffraction dissociation with $\b\,>\,$ 0.4 and the possibility to extract the values of the gluon density from the measurements in this kinematic region is discussed. Shadowing corrections are assessed for both longitudinal and transverse polarised photons and estimates of the different damping factors are given. The relation between diffractive production and the corrections to $F_2$ is alluded to. The evolution of the diffractive structure function is studied and a solution to the difractive evolution equations is proposed.

hep-ph↗

arXiv1995

Landau-Pomeranchuk-Migdal effect for nuclear matter in QCD

Soft photon and gluon radiation off a fast quark propagating through nuclear matter is discussed. The close anology between the Landau - Pomeranchuk - Migdal (LPM) effect in QED and the emission of soft gluons, suggested in ref. \cite{BDPS} for ``hot" plasma, is confirmed and the relation between Mueller's approach and traditional calculations is established. It is shown that perturbative QCD can be applied to take into account the LPM coherent suppression both for photon and gluon induced radiation. The formulae for the photon and gluon radiation densities are presented.

hep-ph↗

arXiv1995

Higher twist corrections to Bjorken sum rule

Some higher twist corrections to the Bjorken sum rule are estimated in the framework of a quark-diquark model of the nucleon. The parameters of the model have been previously fixed by fitting the measured higher twist corrections to the unpolarized structure function $F_2(x, Q^2)$. The resulting corrections to the Bjorken sum rule turn out to be negligible.

hep-ph↗

arXiv1995

THE POMERON: YESTERDAY, TODAY and TOMORROW

These lectures are the review of the main ideas and approaches to the structure of the Pomeron. They are divided in three natural parts: (i) the brief review of the Reggeon Calculus, which was the first attempt to build the effective theory of the strong interaction at high energy. In spite of the fact that this approach turns out to be inconsistent and in lectures we show why, the Reggeon approach was and is the main source of the terminology and phenomenology for high energy ``soft" interactions. (ii) the detail description of the QCD approach to high energy interaction. We try to combine the rigorous approach in perturbative QCD with more simple, intuitive guess based on general properties of QCD to clarify our expectations and predictions. (iii) the outline of my personal opinion what problems will be important in the future. The main reason for the lectures was just the last part to agitate you to think about this difficult but because of that interesting problem. The motto of my lectures is {\it `` there is nothing more exciting than to solve a difficult problem. Pomeron is the one.''}

hep-ph↗

arXiv1994

Renormalons at Low x

The role of infrared and ultraviolet renormalons are discussed in context of leading log(1/x) approximation of perturbative QCD. We generalize the BFKL equation for the case of running coupling QCD constant and show that the uncertainties related to the contribution of infrared renormalons turn out to be smaller than the shadowing correction to the total cross section. The contribution of infrared and ultraviolet renormalons to the BFKL equation are studied, and the solution of the BFKL equation with running coupling constant is discussed.

hep-ph↗