Big-Bang Nucleosynthesis in comparison with observed helium and deuterium abundances - possibility of a non-standard model

Abstract

Comparing the latest observed abundances of 4He and D, we make a ?2 analysis to see whether it is possible to reconcile primordial nucleosynthesis using up-to-date nuclear data of NACRE II and the mean-life of neutrons. If we adopt the observational data of ${}^4_{}$He by Izotov et al., we find that it is impossible to get reasonable concordance against the standard Big-Bang nucleosynthesis. However, including degenerate neutrinos, we have succeeded in obtaining consistent constraints between the neutrino degeneracy and the baryon-to-photon ratio from detailed comparison of calculated abundances with the observational data of ${}^4_{}$He and D: the baryon-to-photon ratio in units of $10^{-10}$ is found to be in the range 6.02 < $\eta^{}_{10}$ < 6:54 for the specified parameters of neutrino degeneracy.