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Neutrino-mixing-generated lepton asymmetry and the primordial He abundance

Physical Review D - Particles, Fields, Gravitation and Cosmology, ISSN: 0556-2821, Vol: 60, Issue: 6, Page: 1-7
1999
  • 28
    Citations
  • 0
    Usage
  • 1
    Captures
  • 0
    Mentions
  • 0
    Social Media
Metric Options:   Counts1 Year3 Year

Metrics Details

  • Citations
    28
    • Citation Indexes
      28
  • Captures
    1

Article Description

It has been proposed that an asymmetry in the electron neutrino sector may be generated by resonant active-sterile neutrino transformations during big bang nucleosynthesis (BBN). We calculate the change in the primordial He yield Y resulting from this asymmetry, taking into account both the time evolution of the ν and ν̄ distribution function and the spectral distortions in these. We calculate this change in two schemes: (1) a lepton asymmetry directly generated by ν mixing with a lighter right-handed sterile neutrino ν, and (2) a lepton asymmetry generated by a ν↔ν or ν↔ν transformation which is subsequently partially converted to an asymmetry in the νν̄ sector by a matter-enhanced active-active neutrino transformation. In the first scheme, we find that the percentage change in Y is between -1% and 9% (with the sign depending on the sign of the asymmetry), bounded by the Majorana mass limit m≲1 eV. In the second scheme, the maximal percentage reduction in Y is 2%, if the lepton number asymmetry in neutrinos is positive; otherwise, the percentage increase in Y is ≲5% for m-m≲10 eV. We conclude that the change in the primordial He yield induced by a neutrino-mixing-generated lepton number asymmetry can be substantial in the upward direction, but limited in the downward direction. ©1999 The American Physical Society.

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