Proton-nucleus interaction at high energy

Abstract

The interaction of high energy protons (between 100 MeV and 20 GeV incident energy) with nuclei is studied in the frame of an intranuclear cascade (INC) model. Particular attention is paid to the energy loss of the projectile and on the emission patterns. It is shown that, in general, the incident proton has left the nucleus before the emission process starts. The latter proceeds first on a rather short time scale and involves fast particles. Progressively the emission rate slows down and the ejected particles are less rapid. The target mass, energy and impact parameter dependences of the energy loss is displayed. As a by-product, we calculate the nuclear stopping power. We investigate the fluctuations in the number of primary collisions, i.e. those suffered by the incoming nucleon, and in the energy loss. Fluctuations in the number of ejectiles are also studied as well as the relationship between primary collisions and the number of fast (grey) particles. The latter number is tentatively related with the number of site vacancies in percolation models. The entropy created inside the target is also calculated. It is shown that the representative point of the system in the (internal energy, entropy) plane spends a relatively long time in the coexistence zone and even in the instability zone corresponding to gas-liquid transition. Implications for these two models of fragmentation are discussed. A preliminary comparison with energy loss measurements in the 3–4 GeV/ c range is performed.