1996A&AS..120C.635M

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_ν>100eV, lifetimes ∼10⁵≤τ_ν≤10¹⁵s, and branching ratios B_γ≥10^–5. We have found no evidence for a radiative decay mode and thus exclude a new region of m_ν/τ_ν/B_γ-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.