Nuclear Structure Effects in Atomic Parity Nonconservationt

L. Wilets

《Chinese Journal of Physics》 32卷6S期 (1994/12) Pp. 1271-1278

並列摘要

Atomic PNC experiments on heavy elements have reached sufficiently high precision to allow for the determination of sin^2θW to such a level as to make a significant contribution to tests of the Standard Model at the level of one loop radiative corrections. In order to extract the weak coupling parameters in experiments on single isotopes, it is necessary to know atomic wave functions in the presence of the PNC mixing term to great accuracy. There have been suggestions to measure PNC effects along an isotopic chain. By taking ratios of observables, complicated atomic structure effects cancel (as in spectroscopic isotope shifts which yield ratios of changes in the charge size). However, the results also depend upon certain features of nuclear structure, such as the spatial distribution of neutrons in the nucleus. To examine the sensitivity to nuclear structure, Pollock, Fortson, Pang and I examined in considerable detail the case of Pb isotopes using various recent relativistic and non-relativistic nuclear model calculations. The spread among present models in the predicted sizes of nuclear structure effects may preclude using Pb isotope ratios to test the Standard Model at better than a one percent level, unless there are adequate independent tests of the nuclear models by various alternative strong and electroweak nuclear probes. On the other hand, sufficiently accurate atomic PNC experiments would provide a unique method to measure neutron distributions in heavy nuclei.