Partial transparency of nuclei and universal properties of proton spectra in relativistic proton-nucleus and nucleus-nucleus collisions

Abstract

On the basis of a model taking into account the effects of nucleus partial transparency, an interpretation of the universal properties of proton inclusive spectra in proton-nucleus and nucleus-nucleus collisions in the incident energy range of 0.5–5 GeV/nucleon is suggested. Within the framework of the rows-on-rows model geometry it is shown that proton spectra resulting from heavy-ion-induced reactions in the target fragmentation region are mainly formed in collisions of projectile peripheral nucleons with the target dense regions. By comparing theory with experimental data the energy dependence of the effective deceleration length of a leading nucleon in nuclear matter is obtained. The universal behaviour of the proton spectra in both the proton-nucleus and nucleus-nucleus reactions is accounted for by the universal mechanism of nuclear matter excitation: a high-energy nucleon loses approximately the same energy, independent of its momentum, per unit of its path length in a target.