Evidence against a 17 keV neutrino fromS35beta decay

We have searched for the effect of a neutrino of mass 17 keV/${\mathit{c}}^2$ in the beta decay of ${}_{}{}^{35}{}_{}{}^{}\mathrm{S}$ with an appartus incorporating a high-resolution solid-state detector and a superconducting solenoid. The experimental mixing probability, ${\sin }^2$θ=-0.0004±0.0008(stat) ±0.0008(syst), is consistent with zero, in disagreement with several previous experiments. Our sensitivity to neutrino mass is verified by measurements with a mixed source of ${}_{}{}^{35}{}_{}{}^{}\mathrm{S}$ and ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$, which artificially produces a distortion in the beta spectrum similar to that expected from the massive neutrino.