Refined big bang nucleosynthesis constraints onΩBandNν

We include corelations between elemental abundances in a Monte Carlo statistical analysis of big bang nucleosynthesis (BBN) predictions, which, along with updated reaction rates and an improved BBN code, lead to tightened constraints on ${\mathrm{\Omega }}_{\mathit{B}}$ and ${\mathit{N}}_{\nu }$. Observational upper limits on the respective primordial ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ and D${+}^3$He fractions of 24% (by mass) and ${10}^{\mathrm{-}4}$ lead to the limits 0.0097${\mathit{h}}^{\mathrm{-}2}$≤${\mathrm{\Omega }}_{\mathit{B}}$≤0.011${\mathit{h}}^{\mathrm{-}2}$ and ${\mathit{N}}_{\nu }$≤3.04. The former argues against purely baryonic galactic halo dark matter, while the latter could put qualitatively new constraints on neutrinos and new physics. Systematic uncertainties in the inferred primordial abundances of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ and D${+}^3$He are required to relax these constraints.