Abstract
We consider the possibility of the lightest sterile neutrino dark matter which has dipole interaction with heavier sterile neutrinos. The lifetime can be long enough to be a dark matter candidate without violating other constraints and the correct amount of relic abundance can be produced in the early Universe. We find that a sterile neutrino with the mass of around MeV and the dimension-five non-renormalisable dipole interaction suppressed by $\Lambda_5 \gtrsim 10^{15}$ GeV can be a good candidate of dark matter, while heavier sterile neutrinos with masses of the order of GeV can explain the active neutrino oscillations.
Highlights
In the context of the standard model (SM) of particle physics, the oscillations between neutrino flavor species and the invisible component of the mass in the Universe cannot find any solution in itself
If three generations of right-handed neutrinos are assumed like other SM fermions, the remaining one right-handed neutrino can be practically decoupled from neutrino oscillation and free from the observations, it can be a candidate for sterile neutrino dark matter [5,6,7]
We find that the lightest sterile neutrino with the mass of around MeV and the dimension-five dipole interaction suppressed by Λ5 ≳ 1015 GeV can be a good candidate for dark matter, and the right amount for DM can be produced through the thermal production in the early
Summary
In the context of the standard model (SM) of particle physics, the oscillations between neutrino flavor species and the invisible component of the mass in the Universe cannot find any solution in itself. While the magnetic moments between the active neutrinos can arise from the dimension-six operators, those between the gauge singlet right-handed neutrinos can arise from the dimensionfive operator [35] Considering that both operators are induced by the same new physics, the dimension-five operator is much less suppressed and may leave observable effects of high scale physics than the dimension-six operator. We find that a sterile neutrino with the mass of around MeV and the dimension-five nonrenormalizable dipole interaction suppressed by Λ5 ≳ 1015 GeV can be a good candidate for dark matter, while heavier sterile neutrinos with masses of the order of GeV can explain the active neutrino oscillations. I or j runs from 1 to 3, and we have mνsj ≃ MνRj due to the mass hierarchy. mνi are eigenvalues of the mass matrix of the light neutrinos, which is generated through the seesaw mechanism [1,2,3,4] as mν
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