Table of contents

A simple Thomas-Fermi method for nuclear matter calculations is used to examine how well the local ¹S₀ potential introduced by Kermode can represent the actual interaction. We compare the results obtained using this potential with those found from Reid soft core potentials.

For pt.I see abstr. A39079 of 1971. Using the Khuri-Trieman model the authors confirm that the gross features of the spectra of eta to 3 pi and K to 3 pi decays can be explained quantitatively in terms of a point interaction for the production vertex and pi pi final state interactions. They make allowances for relativistic effects and Coulomb effects but ignore multiple rescattering corrections and violation of the Delta I=¹/₂ rule. They use S wave pionic amplitudes given by an improved N/D model with some crossing symmetry properties incorporated through Roskies' relations, and deduce the decay amplitudes from Khuri-Treiman theory.

Studies various manifestations of parity mixing in nuclei in the hope of discriminating between weak interaction theories. It is difficult to reconcile the observed circular polarization of the photon in the reaction n+p to d+ gamma with any of the theories considered here. On the other hand, the observed asymmetry of the 110 keV photon of ¹⁹F with respect to the spin direction of the initial state and the circular polarization of the 396 keV photon of ¹⁷⁵Lu are consistent with many of the theories, but rule out those which have a strong Delta T=1 part of the weak Hamiltonian. As an important byproduct of our calculations they present evidence that the effective single-particle potential method of calculating parity mixtures is very good approximation to the more accurate two-nucleon potential method.

Some approximations for obtaining T matrix elements for a sum of several potentials in terms of T matrices for individual potentials are studied. Calculations based on these methods are done for the S wave for the sum of two separable non-local potentials with Yukawa-type form factors and for the sum of two delta function type potentials. The results of these calculations are compared with the corresponding results of first- and second-order Born approximations and with exact calculations.

The photodisintegration of ³He has been studied using a cloud chamber with emphasis on the comparison of the mechanism of the three-body reaction with the theory of Barbour and Phillips (see abstr. A73660 of 1970). Relative yields in two and three-body channels are consistent with theory and the experimental work of Fetisov (1965). Differences are observed however from the theory in the emphasis on the proton-proton and proton-neutron correlation in the final state interaction of the three-body channel.

The four particle transfer ¹¹B(⁷Li, t) reaction has been studied at 12 MeV incident energy. Triton angular distributions corresponding to 18 energy levels in ¹⁵N below 10.8 MeV excitation are presented. Those exhibiting pronounced structures and indicative of direct reaction mechanisms have been compared with Coulomb distorted plane wave model. The angular momenta of the transferred alpha clusters together with their relative reduced widths have been derived. Significant alpha clustering has been observed for six states in ¹⁵N above 9 MeV excitation energy. Negative parity states at 9.152(³/₂^-), 9.827(⁷/₂^-), 9.925(¹/₂^-) and 10.458(⁷/₂^-) MeV are found to possess appreciable 4p-5h character with the predominant configuration (p₃2/)^-1(sd)⁴ mod _j=0.2.

The reaction ³⁰Si( alpha , n)³³S was used to populate levels in ³³S at alpha -particle energies of 6.7, 8.0 and 9.8 MeV. Gamma rays in ³³S were detected in Ge(Li)-NaI(Tl)escape-suppressed spectrometer and a three Ge(Li) Compton polarimeter. The analysis of experimental angular distributions and linear polarizations gave new spin and parity assignments of J^pi =⁵/₂⁺, ³/₂⁺, ⁹/₂⁺, ⁷/₂⁺, ⁹/₂^- and ¹¹/₂^- to the levels at 2866, 3935, 4048, 4094, 4729 and 4866 keV respectively, and (³/₂, ⁵/₂) and (¹/₂, ³/₂) to the levels at 4375 and 4425 keV respectively. Also gamma -ray multipole mixing ratios were unambiguously determined for many transitions from states below 5.0 MeV in excitation. The properties of the positive parity states are compared with predictions of shell model calculations. A description of the negative parity states in terms of the intermediate coupling vibrational model is made.

The states of ⁹⁰Zr up to 5.8 MeV excitation energy have been studied by (e, e') in the momentum transfer range from 0.29 to 1.07 fm^-1. Ground state transition probabilities and transition radii were obtained for the levels excited. Previously published electron scattering data on ⁹⁰Zr are included in the extraction of these parameters. A comparison of results is made with the model independent measurements of the ( gamma , gamma ') reaction for the 2⁺ states. Wherever possible, the results for the electromagnetic transition rates are compared with the iso-scalar transition rates and those obtained form (p, p') reactions. Theoretical calculations are seen to be inadequate to describe the strength of the transitions observed in the present experiment.

The transition rate for leptonic pair production in the decay of 2S state of high-Z mesic atoms is estimated. The electromagnetic decay to e⁺e^- is much smaller than the M1 decay for high Z and is about 2% of the 2E1 decay. The decay into neutrino-antineutrino pairs, which could occur if neutral currents exist, is completely negligible in comparison to other decay processes.

The 300 ton cosmic ray spectrograph (MARS) has been used to measure the vertical momentum spectrum of cosmic ray muons in the momentum range 20-500 GeV/c at sea level.