Study of the Β decay of6He with allowance for second-class currents and the antineutrino mass

The effects of the rest mass of the electron antineutrino are studied with allowance for the induced tensor form-factor Fc of the second-class current according to the Weinberg classification during the Β decay of the6He nucleus. We calculate the contribution of mΝ and Fc to the electron-antineutron angular correlation coefficient AeΝ and the degree of longitudinal polarization Pe of the decay electrons. When mΝ is nonzero, the coefficient AeΝ tends asymptotically to zero both at the beginning and endpoint of the Β spectrum, whether or not the second-class currents are taken into account. The series of qualitatively new experiments planned for the near future to measure the e-Ν correlation for pure Gamow-Teller transitions (the6He nucleus could be a suitable nucleus here) with an accuracy of the order of 1% would allow the available estimate of the form-factor Fc to be improved substantially. © 1990 Plenum Publishing Corporation.