Neutrino-Lifetime Constraints from Neutral Hydrogen in the Galactic Halo

Abstract
Massive neutrinos may dominate the universe's rest mass and compose galactic halos. By requiring that the photoionization of the high-velocity clouds of neutral hydrogen near our galaxy not exceed observational limits, we find that the radiative decay lifetime for ionizing photon production by neutrinos (mν>27.2 eV) composing our galactic halo must exceed 1024 sec.