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

The $\ensuremath{\beta}$-ray angular correlations for the spin alignments of $^{8}\mathrm{Li}$ and $^{8}\mathrm{B}$ have been observed in order to test the conserved vector current (CVC) hypothesis. The alignment correlation terms were combined with the known $\ensuremath{\beta}$-$\ensuremath{\alpha}$ angular correlation terms to determine all the matrix elements contributing to the correlation terms. The weak magnetism term, $7.5\ifmmode\pm\else\textpm\fi{}0.2$, deduced from the $\ensuremath{\beta}$-ray correlation terms was consistent with the CVC prediction $7.3\ifmmode\pm\else\textpm\fi{}0.2$, deduced from the analog-$\ensuremath{\gamma}$ 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 $1.0\ifmmode\pm\else\textpm\fi{}0.3$, while the CVC prediction was $0.1\ifmmode\pm\else\textpm\fi{}0.4$ or $2.1\ifmmode\pm\else\textpm\fi{}0.5$.