Constraining Big Bang lithium production with recent solar neutrino data

TL;DR

This paper uses recent solar neutrino data to better constrain the 3He({ extalpha},{ extgamma})7Be reaction rate, leading to a revised prediction of primordial lithium abundance that exceeds observed levels, impacting Big Bang nucleosynthesis models.

Contribution

It introduces a novel method to constrain Big Bang lithium production by leveraging precise solar neutrino flux measurements and updated reaction rates.

Findings

Revised 3He({ extalpha},{ extgamma})7Be S-factor at solar energies.

New reaction rate at Big Bang energies.

Predicted primordial lithium abundance exceeds observed levels.

Abstract

The 3He({\alpha},{\gamma})7Be reaction affects not only the production of 7Li in Big Bang nucleosynthesis, but also the fluxes of 7Be and 8B neutrinos from the Sun. This double role is exploited here to constrain the former by the latter. A number of recent experiments on 3He({\alpha},{\gamma})7Be provide precise cross section data at E = 0.5-1.0 MeV center-of-mass energy. However, there is a scarcity of precise data at Big Bang energies, 0.1-0.5 MeV, and below. This problem can be alleviated, based on precisely calibrated 7Be and 8B neutrino fluxes from the Sun that are now available, assuming the neutrino flavour oscillation framework to be correct. These fluxes and the standard solar model are used here to determine the 3He(alpha,gamma)7Be astrophysical S-factor at the solar Gamow peak, S(23+6-5 keV) = 0.548+/-0.054 keVb. This new data point is then included in a re-evaluation of the 3He({\alpha},{\gamma})7Be S-factor at Big Bang energies, following an approach recently developed for this reaction in the context of solar fusion studies. The re-evaluated S-factor curve is then used to re-determine the 3He({\alpha},{\gamma})7Be thermonuclear reaction rate at Big Bang energies. The predicted primordial lithium abundance is 7Li/H = 5.0e-10, far higher than the Spite plateau.