Test of the conserved vector current hypothesis by a β-ray angular distribution measurement in the mass-8 system

The β-ray angular correlations for the spin alignments of 8Li and 8B have been observed in order to test the conserved vector current (CVC) hypothesis. The alignment correlation terms were combined with the known β-α angular correlation terms to determine all the matrix elements contributing to the correlation terms. The weak magnetism term, 7.5±0.2, deduced from the β-ray correlation terms was consistent with the CVC prediction 7.3±0.2, deduced from the analog-γ decay measurement based on the CVC hypothesis. However, there was no consistent CVC prediction for the second-forbidden term associated with the weak vector current. The experimental value for the second-forbidden term was 1.0±0.3, while the CVC prediction was 0.1±0.4 or 2.1±0.5.