Regge Poles in QCD and Heavy-Ion Collisions

Abstract

The reggeon approach to interactions of hadrons and nuclei at high energies is reviewed. Basic principles of S-matrix formalism are discussed and complex angular momentum method is presented. Basic properties of Regge poles are outlined. Regge poles are considered from both t- channel and s-channel points of view. The main part of the review is devoted to the Regge poles in QCD. The method of the Wilson-loop path integral is used to calculate trajectories of the Regge poles for \(q - \bar q\) and gluonic states. The problem of the pomeron in QCD is discussed in detail. It is shown how to use the 1/N expansion for classification of the reggeon diagrams in QCD. The role of Regge cuts in reggeon theory is discussed and their importance for high-energy phenomenology is emphasized. Models based on the reggeon calculus, 1/N expansion in QCD, and string picture of interactions at large distances are reviewed and applied to a broad class of phenomena in strong interactions. It is shown how to apply the reggeon approach to small-x physics in deep inelastic scattering. Special attention is devoted to applications of the reggeon approach to high-energy heavy-ion interactions.