Understand
We revisit the state of the light element abundances from big bang nucleosynthesis in early 2024 with particular focus on the derived baryon abundance.
- We find that the largest differences between the final baryon abundances are typically driven by the assumed Deuterium burning rates, characterized in this work by the underlying code.
- The rates from theoretical ab-initio calculations favor smaller baryon abundances, while experimentally-determined rates prefer higher abundances.
- Through robust marginalization over a wide range of nuclear rates, the recently released $\mathtt{PRyMordial}$ code allows for a conservative estimate of the baryon abundance at $\Omega_b h^2 = 0.02218 \pm 0.00055$ (using PDG-recommended light element abundances) in $\Lambda$CDM and $\Omega_b h^2 = 0.02196 \pm 0.00063$ when additional ultra-relativistic relics are considered ($\Lambda$CDM + $N_\mathrm{eff}$).