A study of the interactions of elementary particles

This thesis describes an experiment to investigate the reaction p + p → p + p + π0 at 1 GeV incident proton energy. Optical spark chambers and scintillation counters were used to detect the final state protons. The geometry of the apparatus was such as to select events in which one of the protons had kinetic energy (T) between 50 MeV and 200 MeV and in which the invariant mass (ω) of the other proton + pion lay in the range ~ 1150 MeV to ~ 1300 MeV. Aluminium absorbers between spark chambers were used to measure T to ± 3.6 MeV. Events with 1185 ≤ ω < 1285 MeV were selected for full analysis, and the variation of the reaction cross-section with and T is compared with the predictions of the one pion exchange (OPE) model. The data is in good agreement with calculations which take into account the virtual nature of the exchanged pion. A Chew-Low extrapolation to the one pion exchange pole yields values for the π0 elastic scattering cross-section, averaged over ω in the ranges 1215 - 1245 MeV and 1245 - 1285 MeV, of -5.5±132 mb and 84.2±153 mb. These are compatible with cross-sections calculated from pion nucleon phase shifts. A review of the scope and limitations of the OPE model and, more generally, the peripheral model, is given. This includes a discussion of the influence of absorption processes.