Microscopic, model-space approach to parity nonconservation in compound nuclei

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Abstract
We propose a unified approach to parity nonconservation in compound nuclei in which statistical and collective properties both enter the theory and play an important role. Taking the model space to consist of 0-ħω excitations and motivating our choice of the microscopic effective interaction by the doorway picture of Auerbach, the effect of the one-body parity-violating (PV) interaction enters as a renormalization of the standard two-body PV interaction through collective 0− nuclear excitations. We present semi-quantitative numerical results and compare with previous models. For the model space chosen, the sizes of the contribution from the one- and two-body PV interactions are shown to be comparable. This contrasts to the extreme statistical model (complete mixing in a large model space containing 1-ħω as well as 0-ħω excitations), where the one-body PV interaction dominates. We also find that the dynamics of the 0− resonances and their coupling to nucleons is a more important quantitative consideration than hitherto recognized.