Ph.D Thesis

Ph.D StudentLublinsky Michael
SubjectNonperturbative QCD Effects in Deep Inelastic Scattering
DepartmentDepartment of Physics
Supervisors ASSOCIATE PROF. Boris Blok
PROF. Eugin Levin


This thesis is  devoted to the non-perturbative QCD (quantum chromodin  high energy scattering processes.  In particular, the research is focused on the high parton deynamics) effects displayed  nsity phase of QCD  which is a transition region between perturbative QCD and the  domain of confinement.  Our main hypothesis is that at high energies a system of partons always passes through the stage of high parton density at small distances before it reaches the realm of non-perturbative QCD. A unique situation is met in high density QCD, where the strong coupling constant is small but perturbative methods are not applicable. Remarkably such system can be successfully treated theoretically.

At low densities a parton system  evolves according to linear  equations such as DGLAP and BFKL equations describing parton emission. This emission leads to a growth of the parton density. At large energies, when the density becomes high, the growth is slowed down by parton recombination processes which result in the parton density saturation. Saturation and its experimental signatures  are  major subjects of the thesis.

The main achievement of the thesis is qualitative and quantitative description of the parton density saturation. A particular goal is a performed search for the saturation effects in the present day HERA experimental data on deep inelastic scattering. In addition, strong predictions are given for the saturation effects at higher energies potentially reachable by the LHC and THERA colliders.  Within the very same approach both qualitative and quantitative pictures of the saturation in high energy processes involving nucleus targets are presented which is especially important for the new operating RHIC program.

The research is based on phenomenological models as well as on QCD-derived nonlinear evolution equations valid at high energies.  In the present  work, for the first time these equations are solved numerically. The obtained numerical solutions give us a possibility for  a quantitative description of the parton density saturation.