Big Bang Nucleosynthesis and the Helium Isotope Ratio

Abstract

The conventional approach to search for departures from the standard model of physics during Big Bang Nucleosynthesis involves a careful, and subtle measurement of the mass fraction of baryons consisting of helium. Recent measurements of this quantity tentatively support new physics beyond the standard model but, historically, this method has suffered from hidden systematic uncertainties. In this letter, I show that a combined measurement of the primordial deuterium abundance and the primordial helium isotope ratio has the potential to provide a complementary and reliable probe of new physics beyond the standard model. Using the recent determination of the primordial deuterium abundance and assuming that the measured pre-solar 3He/4He meteoritic abundance reflects the primordial value, a bound can be placed on the effective number of neutrino species, Neff(BBN) = 3.01 (+0.95 -0.76, with 95 per cent confidence). Although this value of Neff supports the standard model, it is presently unclear if the pre-solar 3He/4He ratio reflects the primordial value. New astrophysical measurements of the helium isotope ratio in near-pristine environments, together with updated calculations and experimental values of several important nuclear reactions (some of which are already being attempted), will lead to much improved limits on possible departures from the standard model. To this end, I describe an analysis strategy to measure the 3He I flux emitted from nearby low metallicity H II regions. The proposed technique can be attempted with the next generation of large telescopes, and will be easier to realize in metal-poor H II regions with quiescent kinematics.

5 pages, 2 figures, Accepted for publication in The Astrophysical Journal Letters

References in corpus (6)

• Primordial Nucleosynthesis in the Precision Cosmology Era
• Primordial Nucleosynthesis: from precision cosmology to fundamental physics
• The effects of He I 10830 on helium abundance determinations
• A new determination of the primordial He abundance using the HeI 10830A emission line: cosmological implications
• LUNA: Nuclear Astrophysics Deep Underground
• Probing nuclear rates with Planck and BICEP2

Cited by in corpus (12)

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• Big-Bang Nucleosynthesis After Planck
• The primordial deuterium abundance of the most metal-poor damped Lyman-alpha system
• The PHLEK Survey: A New Determination of the Primordial Helium Abundance
• The Leoncino Dwarf Galaxy: Exploring the Low-Metallicity End of the Luminosity-Metallicity and Mass-Metallcity Relations
• Bayesian estimation of thermonuclear reaction rates for deuterium+deuterium reactions
• Hubble tension in lepton asymmetric cosmology with an extra radiation
• Photometric identification and MMT spectroscopy of new extremely metal-poor galaxies: towards a better understanding of young stellar populations at low metallicity
• Direct Constraints on the Extremely Metal-Poor Massive Stars Underlying Nebular C IV Emission from Ultra-Deep HST/COS Ultraviolet Spectroscopy
• Astrophysical S-factors, thermonuclear rates, and electron screening potential for the ${}^3$He(d,p)${}^4$He Big Bang reaction via a hierarchical Bayesian model
• Big Bang Nucleosynthesis as a probe of non-standard neutrino interactions and non-unitary three-neutrino mixing
• Primordial helium-3 redux: The helium isotope ratio of the Orion nebula