Polarizabilities and parity non-conservation in the Cs atom and limits on the deviation from the standard electroweak model

A semi-empirical calculation of the 6s - 7s Stark amplitude $\alpha$ in Cs has been performed using the most accurate measurements and calculations of the electromagnetic amplitudes available. This is then used to extract the parameters of the electroweak theory from experimental data. The results are: $\alpha =269.0(1.3)a_0^3$, weak charge of Cs $Q_W = -72.41(25){exp} (80){theor}$,deviationfromtheStandardmodel$S = -1.0(.3){exp} (1.0){theor}$andlimitonthemassoftheextraZ-bosoninSO(10)model$M_{Z_x} > 550 GeV$.