Dark Radiation from Neutrino Mixing after Big Bang Nucleosynthesis
ORAL
Abstract
Light dark fermions can mass mix with the Standard Model neutrinos. As a result, through oscillations and scattering, they can equilibrate in the early universe.
Interactions of the dark fermion generically suppress such production at high temperatures but enhance it at later times. We find that for a wide range of mixing angles and interaction strengths equilibration with SM neutrinos occurs at temperatures near the dark fermion mass. For masses below an MeV, this naturally occurs after nucleosynthesis and opens the door to a variety of dark sector dynamics with observable imprints on the CMB and large scale structure, and with potential relevance to the tensions in H0 and S8.
Interactions of the dark fermion generically suppress such production at high temperatures but enhance it at later times. We find that for a wide range of mixing angles and interaction strengths equilibration with SM neutrinos occurs at temperatures near the dark fermion mass. For masses below an MeV, this naturally occurs after nucleosynthesis and opens the door to a variety of dark sector dynamics with observable imprints on the CMB and large scale structure, and with potential relevance to the tensions in H0 and S8.
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Presenters
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Melissa Joseph
University of Utah
Authors
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Melissa Joseph
University of Utah