"Production of resonances by pions"

Abstract

This thesis contains a description of investigations that have been undertaken to examine the inelastic interactions of positively charged pi-mesons with protons. The experiment was carried out at the European Centre for Nuclear Research in Geneva using a separated beam of 5 GeV/c pions produced by the 27 GeV Proton Synchrotron. Pictures were taken of the interactions of the pions with the protons of the 150 cm. British National Hydrogen Bubble Chamber. To analyse the interactions recorded on the films of the chamber a digitized measuring apparatus was constructed. The machine provided data about the interactions encoded in a suitable manner for automatic processing. The numerical and statistical methods used in the computation of the most probable dynamical interpretation of each interaction are given. In the sample of these high multiplicity interactions that have six or seven particles in the final state of the reaction, evidence was found for the production of intermediate particles or resonances. The statistical analysis carried out was consistent with a large production of the well-known resonances N*3/2,pº,wº which decay into two or three particles. Apart from a small number of Xº particles, no evidence was found for a large production of any other resonances including those of which the N*3/2,pº, and wº constitute one of the decay products. The production of resonances in high multiplicity interactions therefore does not proceed by the quasi two-body mode which has been shown to be a dominant feature of the lower multiplicity interaction. It was found that the mechanism of resonance production in k, 5 and 6 body intermediate states could not be described adequately by the statistical model. The distributions of dynamical parameters showed similar effects to those observed for the peripheral production of resonance in the quasi two-body mode of lower multiplicity interactions. It was found that the mechanism of resonance production in 4, 5 and 6 body intermediate states could not be described adequately by the statistical model. The distributions of dynamical parameters showed similar effects to those observed for the peripheral production of resonance in the quasi two-body mode of lower multiplicity interactions.