NEUTRON-TO-PROTON RATIO IN INTERMEDIATE-ENERGY NUCLEAR-REACTIONS

The ratio of inclusive spectra of neutrons and protons in antiproton-, pion-, and proton-nucleus interactions at intermediate energies has b een considered in the framework of the intranuclear cascade (INC) mode l. The ratio predicted by the standard INC model is consistent with th e experimental data for pion- and proton-induced reactions, but contra dicts the ratio obtained in antiproton-nucleus annihilation measuremen ts. It has been shown that for pion-nucleus interactions the n/p ratio is much affected by isotopic effects in pion absorption and mainly de pends on pion charge. Nevertheless, due to the presence of positive, n egative, and neutral pions in antiproton-nucleon annihilation the calc ulated n/p ratio becomes close to the N/Z ratio of the target nucleus. The coalescence of nucleons, preequilibrium emission of particles, in teraction of annihilation pions with the nuclear Coulomb field, neutro n halo effects, and many body annihilation have been considered as pos sible candidates which would affect the n/p ratio in antiproton-nucleu s annihilation. A simple quark counting estimation for the n/p ratio i n many body annihilation has been made.