Nonequilibrium Hydrodynamic Approach to Describing the Emission of High-Energy Secondary Particles in Intermediate-Energy Heavy-Ion Collisions

With the aim of developing the hydrodynamic approach to describing collisions of intermediate-energy heavy ions, it is proposed to solve simultaneously the equations of hydrodynamics and the kinetic equation. This makes it possible to include the nonequilibrium component in the present analysis and to describe successfully experimental data obtained at Institute for Theoretical and Experimental Physics (ITEP, Moscow) for the double-differential cross sections of the emission of cumulative protons, pions, and photons in collisions carbon nuclei with a beryllium target in the energy range between 2.0 and 3.2 GeV per nucleon. The correction for the microcanonical distribution and the contribution of the fragmentation process to the proton yield are taken into account in describing these spectra. The resulting description of these experimental data turns out to be better than the descriptions based on cascade models and models of quantum molecular dynamics. A comparison with other reactions and approaches is performed. It turns out that effects of short-range correlations are included in the proposed approach, since it provides a successful description of experimental hard-photon spectra, which are described within molecular dynamics only upon adding a high-momentum component.