Measurement of Parity Nonconservation and an Anapole Moment in Cesium

Fully relativistic coupled cluster treatment for parity-violating energy differences in molecules

Fully relativistic four-component many-body perturbation and coupled cluster electronic structure calculations including electroweak neutral current corrections are presented for a study of parity-violating effects in chiral molecules. For the chiral molecules H2O2 and H2S2, it is demonstrated that electron correlation contributions to the parity-violating energy shifts are small but critically dependent on the molecular geometry.

Reconciliation of the measurement of parity nonconservation in Cs with the standard model

Contributions from the Breit interaction in atomic structure calculations account for 1.3sigma of the previously reported 2. 5sigma deviation from the standard model in the 133Cs weak charge [S. C. Bennett and C. E. Wieman, Phys. Rev. Lett. 82, 2484 (1999)]. The updated corrections for the neutron distribution reduce the discrepancy further to 1.0sigma. The updated value of the weak charge is Q(W)(133Cs) = -72.65(28)(expt)(34)(theor).

Indications for an extra neutral gauge boson in electroweak precision data

A new analysis of the hadronic peak cross section at LEP 1 implies a small amount of missing invisible width in Z decays, while the effective weak charge in atomic parity violation has been determined recently to 0.6% accuracy, indicating a significantly negative S parameter. As a consequence, the data are described well if the presence of an extra Z' boson, such as predicted in grand unified theories, is assumed. Moreover, the data are now rich enough to study an arbitrary extra Z' boson and to determine its couplings in a model independent way. An excellent fit to the data is obtained in this case, suggestive of a family nonuniversal Z' similar to those predicted in a class of superstring theories.