Refined Big Bang Nucleosynthesis Constraints on $\Omega_{Baryon}$ and   $N_{\nu}$
  We include correlations between elemental abundances in a Monte Carlo statistical analysis of BBN predictions, which, along with updated reaction rates and an improved BBN code, lead to tightened constraints on $\Omega_{B}$ and $N_{\nu}$. Observational upper limits on the primordial \he and $\rm {D + {^3He}}$ fractions of $24 \%$ (by weight) and $ 10^{-4}$ respectively lead to the limits: $0.015 \le \Omega_{B} \le 0.070$, and $N_{\nu} \le 3.04$. The former limit appears to be incompatible with purely baryonic galactic halo dark matter, while the latter puts qualitatively new constraints on neutrinos, and physics beyond the standard model. 
Peter J. Kernan and Lawrence M. Krauss