We calculate the $6s-7s$ parity nonconserving (PNC) $E1\mathrm{}$ transition amplitude $E_{\mathrm{PNC}}$ in cesium. We use an improved all-order technique in the calculation of the correlations and include all significant contributions to $E_{\mathrm{PNC}}.$ Our final value $E_{\mathrm{PNC}}=0.904(1\mathrm{}\pm 0.5\%)\times {10}^{-11}{\mathrm{iea}}_B(-Q_W/N)$ has half the uncertainty claimed in old calculations used for the interpretation of Cs PNC experiments. The resulting nuclear weak charge $Q_W$ for Cs deviates by about $2\sigma$ from the value predicted by the standard model.

• Received 12 April 2002

DOI:https://doi.org/10.1103/PhysRevD.66.076013