IMPROVED INTRANUCLEAR CASCADE MODEL FOR NUCLEON-NUCLEUS INTERACTIONS

The intranuclear cascade (INC) plus evaporation model for nucleon-nucl eus interactions in the 200 MeV-1.2 GeV range is revisited. The standa rd Liege INC model supplemented by the Dresner evaporation-fission mod el is used and shown to give a good overall agreement with experimenta l data, basically neutron double differential cross-sections and resid ue mass spectra. Small systematic discrepancies are identified and sho wn to correspond to the single scattering contribution. Improvements o f the INC model, linked with in-medium cross-sections, refraction of p articles at the nuclear surface, treatment of the Pauli blocking, desc ription of nuclear surface, collision mode and hadronisation time are discussed. The problem of the stopping time at which the cascade model gives place to the evaporation model is examined in detail. The intro duction of a pre-equilibrium step, intermediate between the cascade an d evaporation steps is investigated and shown to bring no significant improvement of the predictions. The production of composites and of in termediate mass fragments is shortly studied, with the help of the sta ndard model, of the three step model mentioned above and of a cascade plus percolation model. (C) 1997 Elsevier Science B.V.