Massive decaying τ neutrino and Big Bang nucleosynthesis

Comparing Big Bang Nucleosynthesis predictions with the light element abundances inferred from observational data, we can obtain the strong constraints on some neutrino properties, e.g. number of neutrino species, mass, Lifetime. Recently the deuterium abundances were measured in high red-shift QSO absorption systems. It is expected that they are close to the primordial values, however, two groups have reported inconsistent values which are different in one order of magnitude. In this paper we show how we can constrain on tau neutrino mass and its lifetime in each case when we adopt either high or low deuterium data. We find that if 0.01 sec less than or similar to tau(v tau) less than or similar to 1 sec and 10 MeV less than or similar to m(v tau) less than or similar to 24 MeV, the theoretical predictions agree with the low D/H abundances. On the other hand if we adopt the high D/H abundances, we obtain the upper bound of tau neutrino mass, m(v tau) less than or similar to 20 MeV. (C) 1998 Elsevier Science B.V. All rights reserved.