The implementation of π production in the Liège intranuclear cascade model (INCL4) for spallation reactions is revisited to alleviate the overestimate of the π yield. Three modifications are proposed for this purpose: a better πN cross section at high energy, the introduction of a π average potential, and the modification of the average mass of the resonance. The π potential is determined from a global fit of a set of data bearing on π production in proton-induced reactions, on π -nucleus and absorption cross sections, and on proton production in π -induced reactions. The resulting π potential is poorly determined in the nuclear interior and agrees with the phenomenological optical-model potentials in the surface region. With these modifications, the predictions of the INCL4 model concerning π production cross sections in proton-induced reactions are considerably improved. Predictions of the improved version for π -nucleus reaction and absorption cross sections and for proton, residue, and fission cross sections in π -induced reactions are also presented and shown to give reasonably good agreement. Neutron production and some aspects of fission in π -induced reactions are also investigated and reasonably well predicted. Effects on the modifications on observables, which are not directly linked with π 's, such as the neutron yield and the residue mass and charge spectra in proton-induced reactions are also investigated and shown to improve the description of these observable quantities. Several results on π production and the relative insentivity to the π potential in the nuclear interior are shown to be consistent with the fact that most π 's are not produced in early collisions. Importance of rescattering in π absorption on nuclei is also pointed out. A comparison is made with the so-called -hole model. Residual discrepancies are identified and are interpreted as due to the lack of π interaction with two nucleons at low energy, to the neglect of quantum motion effects, and to a possible underestimate of rescattering.

Abstract. In many applications of the intranuclear-cascade (INC) model to spallation reactions, all nucleons in the target are assumed to move in a common potential well. However, the potential depth should depend upon nucleon isospin and energy. The present paper describes the first results obtained after the introduction of these features in the Liège INCL3 model. It is shown that such modifications change cascade particle multiplicities significantly but total particle multiplicities are only slightly altered. Nucleon inclusive cross-sections are not modified significantly, except in the region of the quasi-elastic peaks. In particular, the centroid of the peak in neutron double differential cross-sections relative to proton-induced reactions can be sizeably shifted toward larger energy losses, as is observed experimentally. Implications of these results are discussed.PACS. 25.40.-h Nucleon-induced reactions -24.10.-i Nuclear reaction models and methods -24.10.Lx Monte Carlo simulations (including hadron and parton cascades and string breaking models)

The Liège intranuclear cascade (INCL) model is shortly presented. The predictive power of its standard version concerning the description of nucleon-induced spallation reactions in the 200 MeV to 2 GeV range of incident energy is indicated. Current improvements of the model, in particular its extension to higher energies, are emphasized. The capabilities of the model for possible applications in astrophysics, space research and protontherapy are pointed out.