Nucleosynthesis limits on the mass of long lived tau and muon neutrinos

We compute the nucleosynthesis bounds on the masses of stable Dirac and Majorana neutrinos by solving an evolution equation network comprising of all neutrino species which in the Dirac case includes different helicity states as separate species, We will not commit ourselves to any particular value of the nucleosynthesis bound on the effective number of light neutrino degrees of freedom N. but present all our mass bounds as functions of Delta N-nu. For example, we find that the excluded region in the mass of a Majorana mu- or tau-neutrino, 0.29 MeV < m(nu)(M) < 53 MeV corresponding to a bound Delta N-nu < 0.3 gets relaxed to 0.95 MeV < m(nu)(M) < 32 MeV if Delta N-nu < 1.0 is used instead, For the Dirac neutrinos Delta N-nu < 1.0 gives with the present experimental limit nucleosynthesis excludes m(nu tau)(M) > 0.95 MeV and m(nu tau)(D) > 0.37 MeV at 95% CL.