Standard Big-Bang Nucleosynthesis up to CNO with an improved extended nuclear network

TL;DR

This paper enhances Big Bang nucleosynthesis models by expanding the nuclear network to include over 400 reactions up to Sodium, improving reaction rate evaluations, and analyzing implications for primordial element abundances, especially CNO and light elements.

Contribution

It introduces a comprehensive nuclear reaction network up to Sodium with new reaction rates, providing refined primordial abundance predictions and insights into CNO synthesis during BBN.

Findings

Primordial Beryllium abundance increased fourfold.

CNO/H ratio remains stable at ~0.7 x 10^-15.

Li abundance unchanged, still higher than observed.

Abstract

Primordial or Big Bang nucleosynthesis (BBN) is one of the three strong evidences for the Big- Bang model together with the expansion of the Universe and the Cosmic Microwave Background radiation. In this study, we improve the standard BBN calculations taking into account new nuclear physics analyses and we enlarge the nuclear network until Sodium. This is, in particular, important to evaluate the primitive value of CNO mass fraction that could affect Population III stellar evolution. For the first time we list the complete network of more than 400 reactions with references to the origin of the rates, including \approx 270 reaction rates calculated using the TALYS code. Together with the cosmological light elements, we calculate the primordial Beryllium, Boron, Carbon, Nitrogen and Oxygen nuclei. We performed a sensitivity study to identify the important reactions for CNO, 9Be and Boron nucleosynthesis. We reevaluated those important reaction rates using experimental data and/or theoretical evaluations. The results are compared with precedent calculations: a primordial Beryllium abundance increase by a factor of 4 compared to its previous evaluation, but we note a stability for B/H and for the CNO/H abundance ratio that remains close to its previous value of 0.7 \times 10-15. On the other hand, the extension of the nuclear network has not changed the 7Li value, so its abundance is still 3-4 times greater than its observed spectroscopic value.