First-Forbidden Transitions in Parity-Nonconserving Beta Decay

Our previous work on beta-gamma directional correlations is extended to phenomena of nonconservation of parity in beta decay. The parameters, b_LL^'⁽ⁿ⁾, which express the beta-ray angular distributions, are given for first-forbidden transitions of a general interaction, STPVA, where we assume no interferences between STP and VA. All of the possible interferences among the six nuclear matrix elements, M(βσ·r), M(βγ₅), M(βr), M(βα), M(βσ×r), and M(Bᵢⱼ^β) for STP (and the corresponding matrix elements for VA) are taken into account. By using these b_LL^'⁽ⁿ⁾'s, it is easy to express the correction factor of beta spectra, the beta-ray angular distributions from oriented nuclei, and the angular correlations between beta rays and circularly polarized gamma rays from unoriented nuclei in double and triple cascade transitions. The experimental data on the beta decays of Sb¹²⁴ and Au¹⁹⁸ are analyzed.