Further studies on the evidence for a 17-keV neutrino in adoped14germanium detector

We have studied the beta spectrum of ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ using a unique ${}_{}{}^{14}{}_{}{}^{}\mathrm{doped}$ germanium detector. In 1991 an initial report was made of a distortion in the spectrum that could be explained by the emission of a 17-keV neutrino in approximately 1% of the decays. Further tests have shown that the observed distortion was most likely caused by systematic effects related to the detector’s active guard ring. A new measurement with a smaller data sample shows no sign of this distortion. In addition, we find the Q value of ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ decay to be 155.95±0.07(stat.)±0.21(sys.) keV, in disagreement with a previous precision measurement.