Energetic interactions of protons and pions

Abstract

The thesis describes same, features of the interactions of high energy protons and negative pions as observed in nuclear emulsions. A survey is given of the interactions of π(^-)-mesons in the energy range (l00→4,000)MeV, and in particular the optical model analysis is described. It is shown that the optical model can be made to fit the data over the whole energy range. The interactions of 25 GeV protons are described in some detail with references to the interactions of 16 GeV π(^-)-mesons. It is found that there is little difference between the two. Two methods of analysis of the angular distributions of produced particles, the Castagnoli analysis and the Duller-Walker plot, are described together with their application to the proton and pion induced interactions. These analyses suggest that the interaction of the proton with the nucleus is described by the cascade model. The proton makes a series of collisions with nucleons in the nucleus each of which may be inelastic and produce mesons. The struck nucleons emerge from the collisions mainly as grey particles. Those events with zero or one associated grey particle are shown to be single proton-nucleon collisions in agreement with observations of 16 GeV π(^-)-meson interactions. The angular distribution of produced particles is found to be almost isotropic in the centre of mass system, in the laboratory system the primary emerges from many of the interactions at small angles (<5 ). The theory of the so called peripheral interactions, coulomb dissociation and inelastic diffraction scattering, is described and the results of a search for these interactions among the l6 GeV π(^-)-meson events are given. A. small number of such events is found and the cross-section is shown to be small. The emulsions which were exposed to protons were also placed during the exposure in a pulsed magnetic field, of 180 kilograms which was sufficient to produce a detectable curvature. The usefulness of the method is found to be limited by-the degree of distortion and the accuracy of its measurement. The measurements of the 13 GeV proton interactions permitted a value of (49 ± 15) % to be given for the inelasticity.