Deuterium and helium-3 production from massive neutrino decay

A massive (msub(H) > 3.6 MeV) antineutrino can produce free neutrons in the course of its decay, and the neutrons can then bind into deuterium and 3He. If the massive neutrino lifetime is on the order of 103-104s, the above processes occur immediately after the end of primordial nucleosynthesis, when the temperature and baryon density are high enough to allow significant production of deuterium and 3He, but low enough to prevent all of the deuterium and 3He from burning into 4He. The production of deuterium and 3He from the decay of a massive neutrino with mass msub(H) approx. 10-100 MeV and lifetime tausub(H) approx. 103-104s is investigated over a wide range of values for the baryon-to-photon ratio. The photofission of the deuterium from the high-energy photons generated by the neutrino decay is also considered. (author)