A massive neutrino in nuclear beta decay

We have continued our studies of the β‐spectrum of 14C using a germanium detector doped with 14C. There is a feature in the β‐spectrum 17 keV below the endpoint which could be explained by the hypothesis that there is a heavy neutrino emitted in the β‐decay of 14C with a mass of 17±1 keV and an emission probability of 1.26±0.25%. However, we also have performed a high statistics measurement of the inner bremsstrahlung spectrum of 55Fe and find no indication of the emission of a 17‐keV neutrino. We conclude that the origin of the ‘‘kink’’ that has been observed in some recent beta spectral measurements is not a neutrino.