Inside the black box of Big Bang Nucleosynthesis: A comprehensive sensitivity atlas for the precision era

2026/03/31 by Anne-Katherine Burns
Physics and Astronomy · #Neutrino Physics Research #Nuclear physics research studies #Particle physics theoretical and experimental studies #astro-ph.CO #hep-ph

paper · pdf · doi:10.1016/j.physrep.2026.07.001

published as Phys. Rept. 1194 (2026) 1-40 · 89 pages, 39 figures. Published version, with two additional parameters (alpha_EM and r_p) added to Table 4

openalex publication_date 2026/07/11 · openalex created_date 2026/07/12 · openalex updated_date 2026/07/12 · arxiv created 2026/07/31 · arxiv updated 2026/08/03

Abstract

In this study we present a comprehensive sensitivity atlas for Big Bang Nucleosynthesis (BBN) in which we quantify the dependence of the primordial abundances of helium-4, deuterium, and lithium-7 as well as N_\rmeff on variations in 14 fundamental particle physics and cosmological parameters and 63 thermonuclear reaction rates. We use the publicly available BBN code \faGithub \hrefhttps://github.com/vallima/PRyMordial PRyMordial to compute each sensitivity using two nuclear reaction rate compilations and two weak-rate normalization schemes, and provide a model independent reference applicable to Beyond the Standard Model (BSM) models in which MeV scale physics is modified. In addition, we rank each parameter's contribution to the theoretical uncertainty budget. We compare our predictions against the latest observational determinations of the primordial abundances, including a recent LBT measurement of the helium-4 abundance \citeAver:2026dxv which roughly halves the observational uncertainty relative to previous determinations. We present these results both fixing ΔN_{\rm eff} at its Standard Model (SM) value, and allowing it to be a free parameter using the latest uncertainty from the combined CMB+BAO+BBN 2026 value \citeGoldstein:2026iuu. When ΔN_{\rm eff} is allowed to be a free parameter, it dominates the theoretical uncertainty of the helium-4 abundance, highlighting the importance of upcoming observations from the Simons Observatory \citeSimonsObservatory:2025wwn. As illustrative applications, we examine the deuterium tension and the Lithium Problem in light of our sensitivity analysis. The full set of numerical results and figures is publicly available on GitHub \faGithub \hrefhttps://github.com/Anne-KatherineBurns/bbn-sensitivity-atlas bbn-sensitivity-atlas.

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