Neutrino-Dark Sector Equilibration and Primordial Element Abundances

Abstract

After neutrinos decouple from the photon bath, they can populate a thermal dark sector. If this occurs at a temperature above ~100 keV, this can have measurable impacts on light element abundances. We calculate light element abundances in this scenario, studying the impact from rapid cooling of the Standard Model neutrinos, and from an increase in the number of relativistic degrees of freedom $N_{\mathrm{eff}}$, which can occur in the presence of a mass threshold. We incorporate these changes in the publicly available BBN code PRIMAT, using the reaction networks from PRIMAT and from the BBN code PArthENoPE, to calculate Y${}_{\mathrm{P}}$ and D/H. We provide limits from the two different reaction networks as well as with expanded errors to include both results. If electron neutrinos significantly participate in the cooling, we find limits down to temperatures as low as 100 keV. If electron neutrinos are weakly participating (for instance if only the mass eigenstate ${\nu }_3$ equilibrates), cooling places no limits. However, if the dark sector undergoes a "step" in $N_{\mathrm{eff}}$, there can be additional, ${\omega }_b$-dependent constraints. These limits can vary from strong (for low values of ${\omega }_b$) to a mild preference for new physics (for high values of ${\omega }_b$). Future analyses including upcoming CMB data should improve these limits.

arXiv comment6+6 pages

References in corpus (19)

• Sterile Neutrinos as Dark Matter
• The fate of hints: updated global analysis of three-flavor neutrino oscillations
• One percent determination of the primordial deuterium abundance
• Precision big bang nucleosynthesis with improved Helium-4 predictions
• Sterile Neutrinos
• Precision Early Universe Thermodynamics made simple: $N_{\mathrm{eff}}$ and Neutrino Decoupling in the Standard Model and beyond
• Neutrino decoupling beyond the Standard Model: CMB constraints on the Dark Matter mass with a fast and precise $N_{\mathrm{eff}}$ evaluation
• The Atacama Cosmology Telescope: Constraints on Pre-Recombination Early Dark Energy
• Probing Physics Beyond the Standard Model: Limits from BBN and the CMB Independently and Combined
• PArthENoPE reloaded
• A new tension in the cosmological model from primordial deuterium?
• Primordial Deuterium after LUNA: concordances and error budget
• Quantifying uncertainties in primordial nucleosynthesis without Monte Carlo simulations
• A Step in Understanding the $S_8$ Tension
• Joint CMB and BBN Constraints on Light Dark Sectors with Dark Radiation
• Dark Sector Equilibration During Nucleosynthesis
• Resolving conclusions about the early Universe requires accurate nuclear measurements
• Bayesian estimation of thermonuclear reaction rates for deuterium+deuterium reactions
• Dark Radiation from Neutrino Mixing after Big Bang Nucleosynthesis

Cited by in corpus (3)

• LINX: A Fast, Differentiable, and Extensible Big Bang Nucleosynthesis Package
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• Large Neutrino-Dark Matter Interactions: From Effective Field Theory to Ultraviolet Completions