Reconciliation of the Measurement of Parity-Nonconservation in Cs with the Standard Model

Contributions from the Breit interaction in atomic-structure calculations possibly explain the previously reported $2.5\sigma$ deviation from the Standard Model in the $^{133}$Cs weak charge [S.C. Bennett and C.E. Wieman, Phys. Rev. Lett. 82, 2484 (1999)]. The updated value of the weak charge is $Q_{\rm W}(^{133}{\rm Cs}) = -72.65(28)_{\rm expt}(34)_{\rm theor}$. Breit corrections are obtained in third-order relativistic many-body perturbation theory.