Non-Conservation of Parity

Authors(s):A. Salam Publication:Nature Publication Date: Publisher: Citation:Nature No. 4607 447-449 Link:
As mentioned before, experiments with polarized nuclei demonstrate unmistakably that parity is not conserved. The fact that electrons and positrons emitted in beta-decay possess a high degree of longitudinal polarization provides a new tool for the determination of the fundamental beta-interaction. If the 2-state theory with lepton conservation is assumed, the experimental result that positrons are right-polarized implies that positrons are always emitted together with vR-neutrinos. This would mean that the beta-interaction is A and V.
The experimental situation on this question is in confusion. First, most experiments seem to agree on the interaction being S or V plus A or T. This follows from the absence of Fierz interference terms (plus the assumption of time-reversal invariance). The detailed distinction between S or V and T or A is made by electron-neutrino correlation experiments which have nothing to do with violation of parity as such. Experiments with argon-35 seem to show V, experiments with helium-6 show T; neon -19 and neutron data are compatible with either (S,T) or (V,A) combinations. It would appear that if the helium-6 experiments x stay firm, the 2-state theory with lepton conservation will have to be abandoned, notwithstanding its success.