Final-state interactions

Final-state interactions are common ground between nuclear and particle physics. They are fruitful because they enable us to infer properties of two (or more)-body systems, or very short-lived `particles' which are otherwise impossible to reach. There are of course numerous difficulties associated with their study, both experimental and theoretical, but considerable understanding has been accomplished in recent years and a survey is presented here. The study of these interactions is also related further to interesting aspects of the two-body interaction not obtainable through elastic scattering, like off-the-energy shell transitions, aspects of quasi-free scattering, and specific three-body effects, such as three-body forces.