Abstract
It has been recently suggested \cite{Bezrukov:2017ike,Bezrukov:2018wvd} that a cosmic scalar field can completely change the keV-scale sterile neutrino production in the early Universe. Its effect may, for various parameter choices, either suppress sterile neutrino production and make moderate active-sterile mixing cosmologically acceptable, or increase the production and generate considerable dark matter component out of sterile neutrino with otherwise negligible mixing with SM. In this paper we provide analytic estimates complementing and providing details of the numerical calculations performed in \cite{Bezrukov:2018wvd} in the case of resonant amplification of the sterile neutrino production. We also discuss phenomenological and theoretical issues related to the successful implementation of this idea in fully realistic extensions of the Standard Model of particle physics.
Highlights
The numerous dark matter phenomena getting gradually accepted [1] ask for either modification of general relativity or an extension of the Standard Model of particle physics (SM)
Of a special interest are those extensions, which are motivated by particle physics itself, independently from cosmology
Together with x-ray searches, the most recent one is [9]; these constraints exclude the simplest mechanism of sterile neutrino production via the oscillations in the primordial plasma [10] and leave only small regions in the model parameter space cosmologically viable in the situation when the primordial plasma is asymmetric with respect to the lepton charge [11]
Summary
The numerous dark matter phenomena getting gradually accepted [1] ask for either modification of general relativity or an extension of the Standard Model of particle physics (SM). Together with x-ray searches, the most recent one is [9]; these constraints exclude the simplest mechanism of sterile neutrino production via the oscillations in the primordial plasma [10] and leave only small regions in the model parameter space cosmologically viable in the situation when the primordial plasma is asymmetric with respect to the lepton charge [11] While the latter case is still allowed (e.g., within the νMSM setup), the sterile neutrino there does not contribute enough to active neutrino masses, and one may ask for other mechanisms, either extensions or alternatives to those mentioned above. The periodically varying scalar field can induce a parametric resonance phenomenon which dramatically increases the amplitude of neutrino oscillations regardless of active-sterile mixing This mechanism has been studied numerically in Ref. Some lengthy analytic estimates are presented in the Appendix for convenience
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