This work deals with the study of interaction of pions in complex nuclei. The cross sections for inelastic interactions of positive pions with emulsion nuclei have been measured at various pion energies in the (3,3) resonance energy region. The results-have been interpreted in terms of pion-nucleon interaction cross section through isobar formation, using the optical model formalism. Good agreements have been obtained between the experimental and calculated results. The results indicate that the maximum in cross section occurs at about 160 MeV pion incident energy, which is less than the energy at which the (3,3) resonance occurs. This shift in the position of the maximum cross section is attributed to the optical model potential seen by the pion inside the nucleus. Other available experimental data of positive pion interaction cross sections with complex nuclei have been summarized and interpreted successfully by using our model. This model has also been used to obtain the fraction of pions absorbed inside the nucleus in antiproton annihilation. When an antiproton annihilates on a nucleon a number of pions are produced. If, however, the annihilation takes place inside the nucleus, a fraction of pions is absorbed before coming out of the nucleus. The available experimental data on pion multiplicities in T annihilation with hydrogen and emulsion nuclei are compared to obtain the absorption fraction. The results have good agreements with the calculated values in the (3)3) resonance region. The pion-nucleus optical model potential used for our calculation has been obtained on the basis of the theory of Frank-Gammel and Watson in conjunction with the "effective-range" theory of Chew and Low. Many body effects have been taken into account by applying the Pauli exclusion principle to the intermediate state of the nucleon. It has been shown that in the nucleus the peak of the (3,3) resonance in pion-nucleon scattering is considerably reduced and its position shifts towards higher energy. To investigate the mechanism of absorption of pions in complex nuclei, a detailed analysis of the energetic protons produced in the pion induced emulsion stars have been carried out. The stars were produced by (a) direct interaction of 70 MeV positive pions and (b) p¯ annihilation in emulsion. In the latter case, annihilates to produce pions which in turn interact with other nucleons in the nucleus. The absorption of a pion takes place on a pair of nucleons to emit two energetic nucleons. The distributions of energy and opening angles of the energetic proton pairs as well as the energy distribution of the individual energetic protons have been measured. The results are compared with the results obtained from Monte Carlo calculations.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/10785 |
| Date | January 1970 |
| Creators | Chakravartty, Subhas Chandra. |
| Publisher | University of Ottawa (Canada) |
| Source Sets | Université d’Ottawa |
| Detected Language | English |
| Type | Thesis |
| Format | 191 p. |
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