Experimental Test of Baryon Conservation and Neutrino Flux Limits

Abstract

An experiment has been performed in which events not directly attributable to cosmic rays or natural radioactivity were observed for 4500 h in a 200-liter liquid scintillation detector. Shielding from cosmic rays was obtained through anticoincidence techniques and by locating the detector 585 m underground. Background from natural radioactivity was reduced by placing high-energy requirements on acceptable events. The residual signal has been used to establish new lower limits on the stability of nucleons and a new upper limit on the product of the cross section and the electron neutrino (${\ensuremath{\nu}}_{e}, {\overline{\ensuremath{\nu}}}_{e}$) flux whatever its origin, providing its energy is 400 MeV and >30 MeV (${\ensuremath{\nu}}_{e}$) or > 12 MeV (${\overline{\ensuremath{\nu}}}_{e}$). Depending on the assumed decay modes, nucleon lifetime limits in the range 0.6\ifmmode\times\else\texttimes\fi{}${10}^{28}$ to 4\ifmmode\times\else\texttimes\fi{}${10}^{28}$ years were obtained. The upper limits on the neutrino cross-section flux products are $8.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}38}{\ensuremath{\nu}}_{e}$ ${\mathrm{sec}}^{\ensuremath{-}1}$ and $3.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}38}{\overline{\ensuremath{\nu}}}_{e}$ ${\mathrm{sec}}^{\ensuremath{-}1}$.