Abstract
We consider the dark matter model with radiative neutrino mass generation where the Standard Model is extended with three right-handed singlet neutrinos ($N_1$, $N_2$ and $N_3$) and one additional SU(2)$_L$ doublet scalar $\eta$. One of the right-handed neutrinos ($N_1$), being lightest among them, is a leptophilic fermionic dark matter candidate whose stability is ensured by the imposed $\mathbb{Z}_2$ symmetry on this model. The second lightest right-handed neutrino ($N_2$) is assumed to be nearly degenerated with the lightest one enhancing the co-annihilation between them. The effective interaction term among the lightest, second lightest right-handed neutrinos and photon containing transition magnetic moment is responsible for the decay of heavier right-handed neutrino to the lightest one and a photon ($N_2\to N_1 + \gamma$). This radiative decay of heavier right-handed neutrino %to the the lightest one with charged scalar and leptons in internal lines could explain the X-ray line signal $\sim$ $3.5$ keV recently claimed by XMM-Newton X-ray observatory from different galaxy clusters and Andromeda galaxy (M31). The value of the transition magnetic moment is computed and found to be several orders of magnitude below the current reach of various direct dark matter searches. The other parameter space in this framework in the light of the observed signal is further investigated.
Highlights
Framework which invokes this idea of connecting both sectors and has been proposed by Ma [48]
We consider the dark matter model with radiative neutrino mass generation where the Standard Model is extended with three right-handed singlet neutrinos (N1, N2 and N3) and one additional SU(2)L doublet scalar η
One of the right-handed neutrinos (N1), being lightest among them, is a leptophilic fermionic dark matter candidate whose stability is ensured by the imposed Z2 symmetry on this model
Summary
We consider the model proposed by Ma [48] which is the extension of Standard Model with three gauge singlet right-handed neutrinos N1, N2, N3 and extra SU(2)L doublet scalar η. Where hαk, lα and Mk represent Yukawa couplings, lepton doublet and the mass of the right-handed neutrino of type k (Nk) respectively. The tree-level Dirac mass terms for neutrinos cannot be generated since the vacuum expectation value of the doublet η ( η ) is chosen be zero. The right-handed neutrinos in this model can, in principle, be produced in the early universe via different mechanisms The productions of both N1 and N2 in the early universe are assumed to be similar. It is possible to produce correct DM relic density by thermal production the Yukawa coupling is very small. The neutrino mass eigenvalues for the chosen structure of Yukawa couplings of eq (2.8) in this model are written as,. The results of neutrino masses for various points of the parameter space in this model are calculated and found to be compatible with both the abovementioned bounds
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