Experimental limits on massive neutrinos frome+e−annihilations at 29 GeV

A search was made in 29-GeV $e^{+}$ $e^{\mathrm{-}}$ annihilations for massive neutrinos decaying to $e^{\pm }$ $X^{\mp }$(ν) where X is a muon or meson. A 300-${\mathrm{pb}}^{\mathrm{-}1}$ data sample yielded just one candidate event with a mass $m_{\mathrm{eX}}$>1.8 GeV. Significant limits are found for new neutrinos with masses from 1.8 to 6.7 GeV and with mixing parameters in the range 3×${10}^{\mathrm{-}6}$<‖U${\Vert }^2$<1. .AE