Four of five new experiments claim evidence for 17-keV neutrinos

Six years ago, John Simpson at the University of Guelph in Ontario reported a rather disquieting discovery. In the beta decay of tritium, he asserted, a small fraction of decay events appear to produce a neutrino weighing 17 keV. That's 1/30 the mass of the electron-very much larger than anyone was looking for in the many attempts to find evidence for a nonvanishing neutrino mass in the end point of the electron energy spectrum from tritium decay. Having endured the buffets of half a dozen experiments that failed to confirm Simpson's kink, the heavy neutrino has in recent months become the object of renewed experimental and theoretical interest. In the last few months, five new experimental results have been reported: four of them find evidence in support of Simpson's heavy neutrino, but the fifth, finding no such evidence, purports to exclude it at the 99% confidence level. Although this leaves the experimental situation in a state of fervid confusion, the theorists are feeling the need to get busy