The electromagnetic fine-structure constant in primordial nucleosynthesis revisited

Ulf-G. Meißner; Bernard Ch. Metsch; Helen Meyer

doi:10.1140/epja/s10050-023-01131-3

2024 Impact factor 2.8

Hadrons and Nuclei

Open Access

Eur. Phys. J. A (2023) 59: 223
https://doi.org/10.1140/epja/s10050-023-01131-3

Regular Article - Theoretical Physics

The electromagnetic fine-structure constant in primordial nucleosynthesis revisited

Ulf-G. Meißner¹^,2^,3^,4^,5, Bernard Ch. Metsch¹^,3^b and Helen Meyer¹^,2

¹ Helmholtz-Institut für Strahlen- und Kernphysik, Rheinische Friedrich-Wilhelms Universität Bonn, D-53115, Bonn, Germany
² Bethe Center for Theoretical Physics, Rheinische Friedrich-Wilhelms Universität Bonn, 53115, Bonn, Germany
³ Institute for Advanced Simulation (IAS-4), Forschungszentrum Jülich, 52425, Jülich, Germany
⁴ Institut für Kernphysik (IKP-3) and Jülich Center for Hadron Physics, Forschungszentrum Jülich, 52425, Jülich, Germany
⁵ Tbilisi State University, 0186, Tbilisi, Georgia

^b metsch@hiskp.uni-bonn.de

Received: 12 July 2023
Accepted: 20 September 2023
Published online: 4 October 2023

Abstract

We study the dependence of the primordial nuclear abundances as a function of the electromagnetic fine-structure constant $α$ $\alpha$ , keeping all other fundamental constants fixed. We update the leading nuclear reaction rates, in particular the electromagnetic contribution to the neutron-proton mass difference pertinent to $β$ $\beta$ -decays, and go beyond certain approximations made in the literature. In particular, we include the temperature-dependence of the leading nuclear reactions rates and assess the systematic uncertainties by using four different publicly available codes for Big Bang nucleosynthesis. Disregarding the unsolved so-called lithium-problem, we find that the current values for the observationally based $^{2} H$ ${}^{2}\text {H}$ and $^{4} He$ ${}^{4}\text {He}$ abundances restrict the fractional change in the fine-structure constant to less than $2 %$ $2\%$ , which is a tighter bound than found in earlier works on the subject.

© The Author(s) 2023

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