Cosmological Upper Bound on Heavy-Neutrino Lifetimes

Abstract

An upper bound on the lifetime of a massive, neutral, weakly interacting lepton, ${\ensuremath{\nu}}_{H}$, is derived from standard big-bang cosmology. Saturation of the bound and reasonable assumptions about the weak interaction of the ${\ensuremath{\nu}}_{H}$ then yield a prediction of approximately 10 MeV for its mass.