Atomic parity nonconservation: Electroweak parameters and nuclear structure

Abstract

There have been suggestions to measure atomic parity nonconservation (PNC) along an isotopic chain, by taking ratios of observables in order to cancel complicated atomic structure effects. Precise atomic PNC measurements could make a significant contribution to tests of the Standard Model at the level of one loop radiative corrections. 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, we consider the case of Pb isotopes using various recent relativistic and non-relativistic nuclear model calculations. Contributions from nucleon internal weak structure are included, but found to be fairly negligible. The spread among present models in 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.1 12.15.Ji,12.15.Mm,31.10+z Typeset Using REVTEX

Measurement of the Neutron Radius ofPb208through Parity Violation in Electron Scattering

“…A future low-energy test of the standard model may involve the combination of a precise APV experiment along with PV electron scattering to constrain R n [28]. Alternatively, measuring APV for a range of isotopes could provide information on neutron densities [30].…”

“…Atomic parity violation (APV) is also sensitive to R n [10,28,29]. A future low-energy test of the standard model may involve the combination of a precise APV experiment along with PV electron scattering to constrain R n [28].…”

Electrons, new physics, and the future of parity-violation

“…To set the scale of the level of accuracy nuclear theory must achieve to make the isotope ratio measurements useful, supposed we require the uncertainty in the neutron radius term to be as small as the prospective experimental uncertainty in the value of R, namely, 0.1 %. Pollock [25] and Chen and Vogel [26,27] have analyzed the nuclear model spread in ∆X N ; from their analyses, we learn that nuclear theory is at least a factor of two away from achieivng the requisite precision (for a summary of the theoretical situation, see Ref. [13]).…”

Electroweak model and constraints on new physics

“…In the future it could be possible to reduce the theoretical wave function uncertainties by taking the ratios of parity violation in different isotopes [80,94]. There would still be some residual uncertainties from differences in the neutron charge radii, however [95].…”