Big Bang Nucleosynthesis in Crisis?

Authors:
  • NHN. Hata
    N. Hata
  • RSR. J. Scherrer
    R. J. Scherrer
  • GSG. Steigman
    G. Steigman
  • DTD. Thomas
    D. Thomas
  • TWT. P. Walker
    T. P. Walker
  • SBS. Bludman
    S. Bludman
  • PLP. Langacker
    P. Langacker
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Abstract
A new evaluation of the constraint on the number of light neutrino species (N_nu) from big bang nucleosynthesis suggests a discrepancy between the predicted light element abundances and those inferred from observations, unless the inferred primordial 4He abundance has been underestimated by 0.014 +/- 0.004 (1 sigma) or less than 10% (95%C.L.) of 3He survives stellar processing. With the quoted systematic errors in the observed abundances and a conservative chemical evolution parameterization, the best fit to the combined data is N_nu = 2.1 +/- 0.3 (1 sigma) and the upper limit is N_nu < 2.6 (95% C.L.). The data are inconsistent with the Standard Model (N_nu = 3) at the 98.6% C.L.