Search for an Admixture of a 17 keV Neutrino in the β Decay of ³⁵S

Abstract

Abstract The β spectrum of a mass-separated thin 35 S source has been measured with a small-volume Si photodiode. The energy-dependent response function of the total experimental set-up was calculated by the Monte Carlo method without any adjustable parameter. For an admixture of the hypothetical 17 keV neutrino, an upper limit of 0.59% (95% CL) was determined. Neglecting electron scattering on the spectrometer diaphragm was shown to generate a false 17 keV neutrino admixture of 0.3%.