Radiative neutrino decays, SN 1987A, and the submillimeter background.

Abstract

Limits to the radiative decays of massive neutrinos from $\ensuremath{\gamma}$-ray observations of SN 1987A are discussed for the neutrino mass range 100 eV to few MeV. It is shown that balloon-borne spectrometer observations limit the radiative decays of 30 keV-few MeV neutrinos\char22{}${m}_{\ensuremath{\nu}}{\ensuremath{\tau}}_{\ensuremath{\nu}}\ensuremath{\gtrsim}1.1\ifmmode\times\else\texttimes\fi{}{10}^{12}{B}_{\ensuremath{\gamma}}^{\ensuremath{-}1}$ keV sec, where ${B}_{\ensuremath{\gamma}}$ is the radiative branching ratio of the decay\char22{}but that these limits are necessarily \ensuremath{\sim}800 times less stringent than those obtained from the Solar Maximum Mission (SMM) data. Models which invoke the radiative decays of relic neutrinos to generate the submillimeter background are shown to be constrained by the SMM SN 1987A limits.