ANOMALOUS STRUCTURE IN THE BETA-DECAY OF GASEOUS MOLECULAR TRITIUM

We have made high statistics measurements of tritium beta decay to set a limit on the mass of the election antineutrino. The measurements us ed a windowless gaseous source of molecular tritium and a high resolut ion toroidal field magnetic spectrometer. We calibrate the system usin g conversion electrons from the decay of Kr-83m. The best fit value fo r the neutrino mass squared is significantly negative. An anomalous st ructure in the beta decay spectrum in the last 55 eV closest to the en d point causes this result.