A search for radiative neutrino decay from supernovae

We have performed a systematic search for massive neutrinos by looking for the characteristic photon spectrum of a possible radiative decay mode. The search was performed using the COMPTEL instrument aboard the Compton Gamma-Ray Observatory (CGRO) by observing relatively nearby type-II supernovae that are known to be copious producers of neutrinos. This search was sensitive to neutrino masses m(nu) > 100 eV, lifetimes similar to 10(5) less than or equal to tau(nu) less than or equal to 10(15) seconds, and branching ratios B-gamma greater than or equal to 10(-5). We have found no evidence for a radiative decay mode and thus exclude a new region of m(nu)/tau(nu)/B-gamma-parameter space. In addition, we have re-analyzed the null results of the observation made with the Gamma-Ray Spectrometer aboard the Solar Maximum Mission satellite measurements of SN 1987A.