# Nucleosynthesis Predictions and High-Precision Deuterium Measurements

## TL;DR

This paper presents new high-precision measurements of deuterium abundance along with updated nucleosynthesis predictions, confirming consistency with standard Big Bang models and exploring implications for cosmology and physics.

## Contribution

It provides the most precise deuterium measurements to date and updates the AlterBBN code for improved nucleosynthesis predictions, including new physics possibilities.

## Key findings

- Deuterium abundance measured as D/H = 2.55±0.02×10^{-5}
- Updated nucleosynthesis predictions are consistent with observations within 1.7 standard deviations
- No evidence for a dipole in deuterium abundance similar to fine structure constant dipole

## Abstract

Two new high-precision measurements of the deuterium abundance from absorbers along the line of sight to the quasar PKS1937--1009 were presented. The absorbers have lower neutral hydrogen column densities (N(HI) $\approx$ 18\,cm$^{-2}$) than for previous high-precision measurements, boding well for further extensions of the sample due to the plenitude of low column density absorbers. The total high-precision sample now consists of 12 measurements with a weighted average deuterium abundance of D/H = $2.55\pm0.02\times10^{-5}$. The sample does not favour a dipole similar to the one detected for the fine structure constant. The increased precision also calls for improved nucleosynthesis predictions. For that purpose we have updated the public AlterBBN code including new reactions, updated nuclear reaction rates, and the possibility of adding new physics such as dark matter. The standard Big Bang Nucleosynthesis prediction of D/H = $2.456\pm0.057\times10^{-5}$ is consistent with the observed value within 1.7 standard deviations.