Sterile neutrino dark matter as a consequence of nuMSM-induced lepton asymmetry

It has been pointed out in ref.[1] that in the nuMSM (Standard Model extended by three right-handed neutrinos with masses smaller than the electroweak scale), there is a corner in the parameter space where CP-violating resonant oscillations among the two heaviest right-handed neutrinos continue to operate below the freeze-out temperature of sphaleron transitions, leading to a lepton asymmetry which is considerably larger than the baryon asymmetry. Consequently, the lightest right-handed (``sterile'') neutrinos, which may serve as dark matter, are generated through an efficient resonant mechanism proposed by Shi and Fuller [2]. We re-compute the dark matter relic density and non-equilibrium momentum distribution function in this situation with quantum field theoretic methods and, confronting the results with existing astrophysical data, derive bounds on the properties of the lightest right-handed neutrinos. Our spectra can be used as an input for structure formation simulations in warm dark matter cosmologies, for a Lyman-alpha analysis of the dark matter distribution on small scales, and for studying the properties of haloes of dwarf spheroidal galaxies.

Note:

25 pages

dark matter
cosmological neutrinos
physics of the early universe
dark matter: density
neutrino: sterile
lepton: asymmetry
neutrino: right-handed
neutrino: momentum spectrum
temperature: freeze-out
numerical calculations

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Figures(11)

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- JHEP 08 (2008) 008
•
e-Print:
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•
DOI:
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•
DOI:
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Takehiko Asaka
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