We review the evolution of the studies on diffractive processes in the strong interaction over the last 60 years. First, we briefly outline the early developments of the theory based on analyticity and unitarity of the S-matrix, including the derivation and exploration of Regge trajectories and related moving cuts. Special attention is paid to the concept of the Pomeron trajectory introduced for the description of total, elastic and diffractive cross-sections at high energies and to the emergence of the dynamics of multi-Pomeron interactions. The role of large longitudinal distances and color coherent phenomena for the understanding of inelastic diffraction in hadron-hadron scattering and deep inelastic scattering is emphasized. The connection of these phenomena to the cancellation of the contribution of the Glauber approximation in hadron-nucleus collisions and to the understanding of the Gribov-Glauber approximation is explained. The presence of different scales in perturbative QCD due to masses of heavy quarks has led to the emergence of numerous new phenomena including non-universality of the slopes of Regge trajectories made of light and heavy quarks and non-universal energy dependence of elastic cross-sections. The application of perturbative QCD techniques allowed us to calculate from first principles the interaction of small-transverse-size color singlets with hadrons leading to the development of the quantitative theory of hard exclusive reactions and to the successful prediction of many regularities in hard large mass diffraction. It also led to the prediction of the phe-nomenon of complete transparency of nuclear matter in QCD in special processes. The conflict of perturbative QCD with probability conservation for high energy processes of virtual photon-nucleon scattering is explained. Some properties of the new QCD regime are outlined.
All Science Journal Classification (ASJC) codes
- Arts and Humanities(all)
- Physics and Astronomy(all)