A new evaluation of the constraint on the number of light neutrino species (N) from big bang nucleosynthesis suggests a discrepancy between the predicted light element abundances and those inferred from observations, unless the inferred primordial He4 abundance has been underestimated by 0.0140.004 (1) or less than 10% (95% C.L.) of He3 survives stellar processing. With the quoted systematic errors in the observed abundances and a conservative chemical evolution parametrization, the best fit to the combined data is N=2.10.3 (1) and the upper limit is N<2.6 (95% C.L.). The data are inconsistent with the standard model (N=3) at the 98.6% C.L.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)