Measurement of the 6S → 7S Transition Polarizability in Atomic Cesium and an Improved Test of the Standard Model

The ratio of the off-diagonal hyperfine amplitude to the tensor transition polarizability (M_hf/β) for the 6S → 7S transition in cesium has been measured. The value of is then obtained using an accurate semiempirical value of M_hf. This is combined with a previous measurement of parity nonconservation in atomic cesium and previous atomic structure calculations to determine the value of the weak charge. The uncertainties in the atomic structure calculations are updated (and reduced) in light of new experimental tests. The result Q_W = −72.06(28)_expt(34)_theor differs from the prediction of the standard model of elementary particle physics by 2.5σ. [S0031-9007(99)08690-1]