The electromagnetic fine-structure constant in primordial nucleosynthesis revisited

• Published in: The European physical journal. A, Hadrons and nuclei Vol. 59; no. 10
• Main Authors: Meißner, Ulf-G., Metsch, Bernard Ch, Meyer, Helen
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 04.10.2023
• Subjects: Hadrons; Heavy Ions; Nuclear Fusion; Nuclear Physics; Particle and Nuclear Physics; Physics; Physics and Astronomy; Regular Article - Theoretical Physics
• ISSN: 1434-601X; 1434-601X
• DOI: 10.1140/epja/s10050-023-01131-3

We study the dependence of the primordial nuclear abundances as a function of the electromagnetic fine-structure constant α , 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 -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 and 4 He abundances restrict the fractional change in the fine-structure constant to less than 2 %  , which is a tighter bound than found in earlier works on the subject.