Experimental and Theoretical Studies of Proton Induced Nuclear Spallation

Abstract

Progress in the understanding of the proton induced disintegration of the atomic nuclei at the GeV incident energy range related to the achievements of the PISA (Proton Induced SpAllation) experiment is reported. The scientific motivation of the spallation research is given. Experimental technique as well as the measured distributions of the double differential cross section (d2σ / dΩdE) for spallation products in broad range of bombarding energies and for target nuclei of various masses are presented. Interpretation of obtained results in the frame of a classical two step model utilizing the mechanism of intranuclear cascade for the first phase of the reaction and the statistical evaporation from the thermalized target-like remnant for a second step is described. Significant deficiencies of two step approach in reproducing of the experimental observables related to the dynamic stage of the reaction is indicated. Search for the features of alternatives scenarios of spallation process with the use of phenomenological models is undertaken and the conclusion indicating the need of inclusion to the theoretical description of the reaction the intermediate compound and excited fragments is derived. A new microscopical model (Spallation Model with Cascade++) of the first dynamical phase of a pA reaction is developed. Besides of the binary nuclear interactions a mechanism consisting in a Dynamic Clustering in Nuclear Medium (DCNM) is postulated. The resulting improvement in the theoretical description of the distributions of the Light Charged Particles (LCP) in comparison to the models where only binary interactions are considered is shown.