transition in atomic cesium.*

Measurements of atomic parity violation (APV), mediated by the weak interaction, facilitate determinations of the weak charge Q_w, as well as the weak mixing angle, θ_w. These values provide a unique test of the standard model at low momentum transfers. Determination of Q_w relies on theoretical calculations as well as precision measurements of a parity-violating optical transition relative to another known transition. The most precise measurement of APV was that of Wood et al. [1], who measured the ratio of the parity non-conserving (PNC) transition amplitude (E_PNC) relative to the vector Stark polarizability (β) in atomic cesium. Contention between the two techniques that are used to determine β, see [2], requires resolution for precise determination of Q_w. Here we discuss our recent efforts to correct the discrepancy including a measurement of the dc Stark shift of the 7s  ²S_1/2 state in atomic cesium [3]. We measure the Stark shift by offset phase locking a laser to a frequency comb source and drive a Doppler free two-photon transition. We use theoretical calculations of Tan et al. [4] (for E1 matrix elements to high n states) to recalculate the 〈7s‖r‖7p_1/2〉and 〈7s‖r‖7p_3/2〉  reduced dipole matrix elements and then use these new matrix elements to reevaluate β.

[1] C. S. Wood, S. C. Bennett, D. Cho, B. P. Masterson, J. L. Roberts, C. E. Tanner, and C. E. Wieman, Science 275, 1759 (1997).

[2] G. Toh, A. Damitz, C. E. Tanner, W. R. Johnson, and D. S. Elliott, Phys. Rev. Lett. 123, 073002 (2019).

[3] J. Quirk, A. Jacobsen, A. Damitz, C. E. Tanner, and D. S. Elliott,  arXiv:2311.09169 (2023).

[4] H. B. Tran Tan and A. Derevianko, Phys. Rev. A 107, 042809 (2023).