E. Levin

Parton saturation and Npart scaling of semi-hard processes in QCD

Abstract We argue that the suppression of high p t hadrons discovered recently in heavy ion collisions at RHIC may be a consequence of saturation in the color glass condensate. We qualitatively and semi-quantitatively describe the data, in particular, the dependence upon the number of nucleon participants. We show that if parton saturation sets in at sufficiently small energy, then in nucleus–nucleus collisions at RHIC and LHC energies the cross sections of semi-hard processes should scale approximately with the number of participants, N part . Our results provide a possible explanation of both the absence of apparent jet quenching at SPS energies and its presence at RHIC. Under the same assumption we predict that in semi-central and central pA ( dA ) collisions at collider energies the dependence of semi-hard processes on the number of participating nucleons of the nucleus will change to ∼( N part A ) 1/2 . The forthcoming data on dA collisions will provide a crucial test of this description.

Solution to the evolution equation for high parton density QCD

Abstract In this paper a solution is given to the non-linear equation which describes the evolution of the parton cascade in the case of the high parton density. The related physics is discussed as well as some applications to heavy ion–ion collisions.

New scaling in high energy DIS

Abstract We develop a new approach for solving the nonlinear evolution equation in the low x B region and show that the remarkable “geometric” scaling of its solution holds not only in the saturation region, but in much wider kinematical region. This is in a full agreement with experimental data (Golec-Biernat, Kwiecinski and Stasto).

Onset of classical QCD dynamics in relativistic heavy ion collisions

The experimental results on hadron production obtained recently at RHIC offer a new prospective on the energy dependence of the nuclear collision dynamics. In particular, it is possible that parton saturation---the phenomenon likely providing initial conditions for the multiparticle production at RHIC energies---may have started to set in central heavy ion collisions already around the highest CERN SPS energy. We examine this scenario, and make predictions based on high density QCD for the forthcoming

QCD saturation and deuteron–nucleus collisions

\sqrt{s}=22

Towards a symmetric approach to high energy evolution: Generating functional with pomeron loops

GeV run at RHIC.

Nonlinear evolution and saturation for heavy nuclei in DIS

Abstract We make quantitative predictions for the rapidity and centrality dependencies of hadron multiplicities in dA collisions at RHIC basing on the ideas of parton saturation in the color glass condensate.

Towards a new global QCD analysis: low x DIS data from non-linear evolution

Abstract We derive an evolution equation for the generating functional which accounts for processes for both gluon emission and recombination. In terms of color dipoles, the kernel of this equation describes evolution as a classical branching process with conserved probabilities. The introduction of dipole recombination allows one to obtained closed loops during the evolution, which should be interpreted as pomeron loops of the BFKL pomerons. In comparison with the emission, the dipole recombination is formally 1 / N c 2 suppressed. This suppression, nevertheless, is compensated at very high energies when the scattering amplitude tends to its unitarity bound.

A linear evolution for non-linear dynamics and correlations in realistic nuclei

Abstract The nonlinear evolution equation for the scattering amplitude of colour dipole off the heavy nucleus is solved in the double logarithmic approximation. It is found that if the initial parton density in a nucleus is smaller then some critical value, then the scattering amplitude is a function of one scaling variable inside the saturation region, whereas if it is greater then the critical value, then the scaling behaviour breaks down. Dependence of the saturation scale on the number of nucleons is discussed as well.

Balitsky's hierarchy from Mueller's dipole model and more about target correlations

Abstract. A new approach to global QCD analysis is developed. The main ingredients are two QCD-based evolution equations. The first one is the Balitsky-Kovchegov non-linear equation, which sums higher twists while preserving unitarity. The second equation is linear and it is responsible for the correct short distance behavior of the theory, namely it includes the DGLAP kernel. Our approach allows for extrapolation of the parton distributions to the very high energies available at the LHC as well as very low photon virtualities,