Theory of coherent production on nuclei

The theory of nuclear reactions of the type a+A→a*+A, where a is a hadron and a* one of its multi-particle excitations is reviewed. In coherent reactions the nucleus A remains in its ground state. Production experiments with nuclear targets are usually designed to give information which cannot be obtained from experiments with hydrogen targets alone. The main emphasis is on the determination of i) strong and electromagnetic production amplitudes on nucleons and of ii) cross sections for unstable particles on nucleons. The experimental data are usually interpreted with the Glauber model but it must be remembered that there is no universal formula valid for all types of production reactions. The author in particular discusses phenomena which might be important for the proper interpretation of recent experiments. i) The helicity structure of the underlying nucleon amplitudes which is crucial for determining the nuclear form factor. ii) The production mechanism which is not necessarily of the one-step type. For many channels multi-step production is expected. iii) The possible corrections to the description of the propagation of high energy particles in nuclear matter. (Auth.)