Search for heavy neutrinos in the beta decay of 35S. Evidence against the 17 keV heavy neutrino

Abstract A precise measurement of the beta-ray spectrum of 35 S has been carried out using a Si(Li) spectrometer system to look for the signiture of heavy neutrino emission. The results are consistent with no heavy neutrino admixture, and the resulting upper limits for the mixing | U eH | 2 ≲0.3% were determined in the mass range 10–50 keV.