High-accuracy nuclear-spin-dependent parity-violating amplitudes in Cs 133

Relativistic coupled-cluster (RCC) theory at the singles and doubles approximation has been implemented to estimate nuclear-spin-dependent (NSD) parity-violating (PV) electric dipole (E1) transition amplitudes (E1PVNSD) among hyperfine levels of the 6sS1/22→7sS1/22 transition in Cs133. To validate our calculations, we reproduce the Dirac-Hartree-Fock values and results from the combined coupled-Dirac-Hartree-Fock and random phase approximation (CPDF-RPA) method reported earlier. Contributions from the double-core-polarization (DCP) effects with the CPDF-RPA method were found to be between 3% and 12% among different hyperfine levels. We derived a generalized expression for E1PVNSD, which helped incorporate both the NSD PV Hamiltonian and E1 operator simultaneously in the perturbative approach to account for the DCP contributions. The RCC method subsumes the CPDF-RPA and DCP effects in addition to contributions from the Brückner pair correlations and normalization of the wave functions and correlations among them. To improve accuracy of the E1PVNSD amplitudes further, we replace the ab initio values of the E1 matrix elements and energies by their experimental values via a sum-over-states approach.