Search for admixture of heavy neutrinos with masses between 5 and 55 keV

Abstract

Using a magnetic spectrometer at a momentum resolution of 0.3%, we have studied the beta spectrum from $^{35}\mathrm{S}$. We do not see evidence for the admixture of a heavy neutrino to the usual light (m\ensuremath{\simeq}0) \ensuremath{\nu}${\ifmmode \tilde{}\else \~{}\fi{}}_{\mathrm{e}}$ accompanying beta decay, in the mass range between 5 and 50 keV, with a limit for the mixing strength of \ensuremath{\Vert}U${\ensuremath{\Vert}}^{2}$3\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}3}$ (90% confidence limit).