Abstract
We investigate a ℤ3 symmetric model with two-loop radiative neutrino masses. Dark matter in the model is either a Dirac fermion or a complex scalar as a result of an unbroken ℤ3 symmetry. In addition to standard annihilation processes, semi-annihilation of the dark matter contributes to the relic density. We study the effect of the semi-annihilation in the model and find that those contributions are important to obtain the observed relic density. The experimental signatures in dark matter searches are also discussed, where some of them are expected to be different from the signatures of dark matter in ℤ2 symmetric models.
Highlights
The DM mass dependence of the total neutrino flux is shown in figure 7 where both σSI and σSD are fixed to 10−45 cm2, as we evaluated for the large Yukawa parameter sets, and the sum of the branching ratios in eq (3.17) is taken as 1
We have considered a model with Z3 symmetry
The neutrino masses are generated at the two-loop level and the known neutrino mass scale has been derived with a reasonable value for the coupling strength
Summary
The model considered here is quite simple. It was proposed and discussed briefly in ref. [48]. We introduce two Dirac fermions ψi (i = 1, 2), and two scalar bosons η and χ to the SM with Z3 symmetry and lepton number as shown in table 1.2 The new scalars η and χ are SU(2)L doublet and singlet, respectively. The phases of μχ and μχ are absorbed by the field redefinitions of η and χ This scalar potential is basically the same as that in the Z3 DM model in ref. The parameters μ2φ and λ1 are determined by the vacuum expectation value and the mass of the SM Higgs boson, φ (≈ 174 GeV) and mh, as μ2φ = −m2h/2 ≈ −(89 GeV) and λ1 = m2h/ φ 2 ≈ 0.5. We can take m2L, m2H , sin α, λ2, λ3, λ4, λχ, λφχ, ληχ, μχ as the new independent parameter set in the scalar potential
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