Color screening and color transparency in hard nuclear processes

Abstract

We explain why color screening is expected to be essential in the interaction of hadrons in QCD both in perturbative and nonperturbative domains. Current ideas and approximations characteristic for the color transparency phenomenon in QCD are discussed. Space-time development of hard processes at large and moderate energies is considered. We show that Bjorken scaling in deep inelastic processes at small x Bj is another form of the color transparency. We argue that the color transparency phenomenon is an extension of the known similarity between QCD and QED for hard processes to the exclusive processes. The possible role of the color screening in the microscopic nuclear structure is also discussed. It is shown that color transparency phenomenon should be manifested in the wide range of phenomena including nuclear shadowing in the deep inelastic processes at small x Bj, large angle quasielastic lepton (hadron) high energy processes off nuclei, the EMC effect at x Bj > 0.3, diffractive electro and photo production of charmonium states, production of nucleon spectators in high-energy central nucleus-nucleus collisions, etc.