Number 21 (Story #2), February 13, 1991 by Phillip F. Schewe and Ben Stein EVIDENCE FOR A NEUTRINO WITH A MASS OF 17 keV has accumulated in labs at Oxford, Ontario (Guelph), and Berkeley (Eric Norman, LBL, 415-486-5088). Beta decay experiments with nuclei such as tritium, sulphur-35, and carbon-14 have uncovered anomalies in the energy spectrum of the electrons coming from the decays. The shape of the spectra has been interpreted to mean that the beta-decaying nuclei usually emit a neutrino which has little or no mass, but that occasionally (a few percent of the time) a neutrino with a mass of 17 keV is being emitted. This may be a tau neutrino---whose mass, along with that of the electron neutrino and the mu neutrino, has not been definitively measured---or it may be some new kind of neutrino. The discovery of so massive a neutrino would have implications for particle physics and for cosmology. (New Scientist, 2 Feb. 1991.)