Correlation effects in the parity-nonconserving6s→7stransition in cesium

The amplitude of the parity-nonconserving (PNC) electric-dipole transition 6s→7s in cesium is calculated to third order in many-body perturbation theory. Inclusion of the corresponding corrections in calculations of parity-conserving transition amplitudes and atomic hyperfine constants leads to agreement with experiment at a level under 5%. We obtain a value of 0.951${\mathrm{iea}}_0$×${10}^{\mathrm{-}11}$ $Q_W$/-N with an estimated error of 5% for the PNC amplitude. A determination of the Weinberg angle is made by combining the present calculation with recent measurements of the PNC amplitude: the result is ${\sin }^2$ ${\mathrm{\theta }}_{\mathrm{W}}$=0.229 ${\mathrm{}\left(24\right)\mathrm{}}_{\mathrm{expt}}$ ${\mathrm{}\left(16\right)\mathrm{}}_{\mathrm{theor}}$. Issues involved in improving the accuracy of the calculations of atomic properties of cesium are discussed.