RE-DETERMINATION OF BETA-ENERGY OF TRITIUM AND ITS RELATION TO NEUTRINO REST MASS AND GAMOW-TELLER MATRIX ELEMENT

The upper energy limit of the β-particles of 3H is determined with a retarding field spectrometer. Without having to relyon any assumptions concerning the structure of the source or of the resolving power of the instrument, an upper limit (80 % confidence) of 200 eV for the rest mass of the antineutrino or its Fermi energy is found. Assuming that this mass is actually zero, a value for the maximum β-energy of 18.72±0.05 keV is found. The corresponding ft value is 1159±11 s. This result together with the very much lower half-life of the neutron by Christensen et al. gives a value of the square of the GT matrix element of 2.84±0.06. This practically removes the discrepancy with the prediction of the PCAC hypothesis concerning the enhancement of the GT matrix element by pion exchange. © 1969.