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Updated: Aug 2, 2025

Setting Limits on Supersymmetry Using Simplified Models
Published on: November 15, 2013
Indications for a Nonzero Lepton Asymmetry from Extremely Metal-Poor Galaxies
Anne-Katherine Burns1, Tim M P Tait1, Mauro Valli2
1Department of Physics and Astronomy, University of California, Irvine, California 92697, USA.
Abstract:
The recent measurement of helium-4 from the near-infrared spectroscopy of extremely metal-poor galaxies by the Subaru Survey may point to a new puzzle in the early Universe. We exploit this new helium measurement together with the percent-level determination of primordial deuterium, to assess indications for a nonvanishing lepton asymmetry during the big bang nucleosynthesis era, paying particular attention to the role of uncertainties in the nuclear reaction network. A cutting-edge Bayesian analysis focused on the role of the newly measured extremely metal-poor galaxies, jointly with information from the cosmic microwave background, suggests the existence of a nonzero lepton asymmetry at around the 2σ level, providing a hint for cosmology beyond lambda cold dark matter. We discuss conditions for a large total lepton asymmetry to be consistently realized in the early Universe.
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