A new solar neutrino channel for grand-unification monopole searches

Abstract

We identify a previously untapped discovery channel for grand-unification monopoles, arising from their ability to catalyse the direct decay of protons into monoenergetic 459 MeV antineutrinos within the Sun. Previous analyses omit this possibility as it necessarily involves an electroweak suppression factor, and instead search for the unsuppressed 20-50 MeV neutrinos produced via two-stage proton decays. By accounting for the relative difference in interaction cross section and experimental background at typical neutrino detection experiments, we demonstrate that this new channel in fact possesses greater discovery potential. As a case in point, using 5326 live days of Super-Kamiokande exposure we find that $2\;\sigma$ ($3\;\sigma$) deviations in the 20-50 MeV channel are amplified to $3\;\sigma$ ($4.6\;\sigma$) deviations in the 459 MeV case. Exploiting correlations between these two channels may also offer even greater statistical power.