Kavli Affiliate: Masahiro Kawasaki
| First 5 Authors: Kentaro Kasai, Kentaro Kasai, , ,
| Summary:
The existence of a large primordial neutrino asymmetry is an intriguing
possibility, both observationally and theoretically. Such an asymmetry can lead
to the resonant production of $mathrmkeV$-scale sterile neutrinos, which are
a fascinating candidate for dark matter. In this paper, we comprehensively
revisit the resonant production processes with a refined numerical analysis,
adopting a dynamical discretization of momentum modes to take care of the
sharpness of the resonance. We find parameter regions consistent with X-ray and
Lyman-$alpha$ constraints for lepton-to-entropy ratio $gtrsim
mathcalO(10^-3)$ and $m_nu_sgtrsim 20$,keV. We also explore the
Affleck-Dine mechanism as a possible origin for such asymmetries. While
previous studies considered resonant production after lepton number generation,
we numerically investigate cases where a fraction of sterile neutrinos is
produced during lepton number injection. In this regime, some parameter sets
can shorten the free-streaming length and reduce the required mixing angle to
match the observed dark matter abundance, thereby mitigating the observational
constraints.
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