RESONANCE PRODUCTION ON NUCLEI AT HIGH-ENERGIES - NUCLEAR-MEDIUM EFFECTS AND SPACE-TIME PICTURE

The influence of nuclear matter on the properties of coherently produc ed resonances is discussed. It is shown that, in general, the mass dis tribution of resonance decay products has a two-component structure co rresponding to decay outside and inside the nucleus. The first (narrow ) component of the amplitude has a Breit-Wigner form determined by the vacuum values of mass and width of the resonance. The second (broad) component corresponds to interactions of the resonance with the nuclea r medium. It can be also described by a Breit-Wigner shape with parame ters depending, e.g. on the nuclear density and on the cross section o f the resonance-nucleon interaction. The resonance production is exami ned both at intermediate energies, where interactions with the nucleus can be considered as a series of successive local rescatterings, and at high energies, E > E-crit, where a change of interaction picture oc curs. This change of mechanisms of the interactions with the nucleus i s typical for the description within the Regge theory approach and is connected with the non-local nature of the reggeon interaction. (C) 19 97 Elsevier Science B.V.