Improved intranuclear cascade model for nucleon-nucleus interactions

Abstract

The intranuclear cascade (INC) plus evaporation model for nucleon-nucleus interactions in the 200 MeV–1.2 GeV range is revisited. The standard Liège INC model supplemented by the Dresner evaporation-fission model is used and shown to give a good overall agreement with experimental data, basically neutron double differential cross-sections and residue mass spectra. Small systematic discrepancies are identified and shown to correspond to the single scattering contribution. Improvements of the INC model, linked with in-medium cross-sections, refraction of particles at the nuclear surface, treatment of the Pauli blocking, description 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 introduction of a pre-equilibrium step, intermediate between the cascade and evaporation steps is investigated and shown to bring no significant improvement of the predictions. The production of composites and of intermediate mass fragments is shortly studied, with the help of the standard model, of the three step model mentioned above and of a cascade plus percolation model.