It is shown in a model-independent fashion that, even without the conserved vector current test by extracting the shape factors from the observed $e^{\mp }$ energy spectra in the beta decays of ${}_{}{}^{12}{}_{}{}^{}\mathrm{B}$ and ${}_{}{}^{12}{}_{}{}^{}\mathrm{N}$, the validity of conservation of vector current and partial conservation of axial vector current and the absence of second-class axial currents have now been individually confirmed by the combination of the muon capture data and the results of the recent asymmetry measurements. On the other hand, it is found that the presence of appreciable meson-exchange corrections does not cause a serious discrepancy between the asymmetry data and the Cohen-Kurath nuclear model after the spin-quadrupole-moment term (from the $L=2\mathrm{}$ component of the lepton wave functions) and all the theoretical uncertainties are also taken into account.

RADIOACTIVITY CVC, PCAC, and no second-class axial vector current, tested individually; meson-exchange corrections, compatibility with the Cohen-Kurath nuclear wave functions.

• Received 1 December 1978

DOI:https://doi.org/10.1103/PhysRevC.20.814