No Arabic abstract
We study a light dark matter in a radiative neutrino model to explain the X-ray line signal at about $3.5$ keV recently reported by XMN-Newton X-ray observatory using data of various galaxy clusters and Andromeda galaxy. The signal requires very tiny mixing between the dark matter and an active neutrino; $sin^2 2thetaapprox 10^{-10}$. It could suggest that such a light dark matter cannot contribute to the observed neutrino masses if we use the seesaw mechanism. In other words, neutrino masses might come a structure different from the dark matter. We propose a model in which Dirac type active neutrino masses are induced at one-loop level. On the other hand the mixing between active neutrino and dark matter are generated at two-loop level. As a result we can explain both the observed neutrino masses and the X-ray line signal from the dark matter decay with rather mild hierarchy of parameters in TeV scale.
We study an exciting dark matter scenario in a radiative neutrino model to explain the X-ray line signal at $3.55$ keV recently reported by XMN-Newton X-ray observatory using data of various galaxy clusters and Andromeda galaxy. We show that the required large cross section for the up-scattering process to explain the X-ray line can be obtained via the resonance of the pseudo-scalar. Moreover this model can be compatible with the thermal production of dark matter and the constraint from the direct detection experiment.
We discuss the 3.55 keV X-ray line anomaly reported by XMN-Newton X-ray observatory using data of various galaxy clusters and Andromeda galaxy in a radiative neutrino model, in which the mixing between the active neutrino and the dark matter is generated at two-loop level after the spontaneous breaking of $Z_2$ symmetry. It might provide us a natural explanation of its tiny mixing ${cal O}(10^{-10})$, which is observed by their experiments. Such an Abelian discrete symmetry plays a crucial role in differentiating the TeV scale Majorana field from our dark matter, whose mass is expect to be around 7.1 keV.
We consider an extension of Zee-Babu model to explain the smallness of neutrino masses. (1) We extend the lepton number symmetry of the original model to local $B-L$ symmetry. (2) We introduce three Dirac dark matter candidates with flavor-dependent $B-L$ charges. After the spontaneous breaking of $B-L$, a discrete symmetry $Z_6$ remains, which guarantees the stability of dark matter. Then the model can explain the 3.5 keV X-ray line signal with decaying dark matter. We also introduce a real scalar field which is singlet under both the SM and $U(1)_{B-L}$ and can explain the current relic abundance of the Dirac fermionic DMs. If the mixing with the SM Higgs boson is small, it does not contribute to DM direct detection. The main contribution to the scattering of DM off atomic nuclei comes from the exchange of $U(1)_{B-L}$ gauge boson, $Z$, and is suppressed below current experimental bound when $Z$ mass is heavy ($gtrsim 10$ TeV). If the singlet scalar mass is about 0.1--10 MeV, DM self-interaction can be large enough to solve small scale structure problems in simulations with the cold DM, such as, the core-vs-cusp problem and too-big-to-fail problem.
We study the phenomenology of a keV sterile neutrino in a supersymmetric model with $U(1)_R-$ lepton number in the light of a very recent observation of an X-ray line signal at around 3.5 keV, detected in the X-ray spectra of Andromeda galaxy and various galaxy clusters including the Perseus galaxy cluster. This model not only provides a small tree level mass to one of the active neutrinos but also renders a suitable warm dark matter candidate in the form of a sterile neutrino with negligible active-sterile mixing. Light neutrino masses and mixing can be explained once one-loop radiative corrections are taken into account. The scalar sector of this model can accommodate a Higgs boson with a mass of $sim$ 125 GeV. In this model gravitino is the lightest supersymmetric particle (LSP) and we also study the cosmological implications of this light gravitino with mass $sim mathcal O$(GeV).
We present a simple model for a 7 keV scalar dark matter particle which also explains the recently reported anomalous peak in the galactic X-ray spectrum at 3.55 keV in terms of its two photon decay. The model is arguably the simplest extension of the Standard Model, with the addition of a real scalar gauge singlet field subject to a reflection symmetry. This symmetry breaks spontaneously at an energy scale of a few MeV which triggers the decay of the dark matter particle into two photons. In this framework, the Higgs boson of the Standard Model is also the source of dark matter in the Universe. The model fits the relic dark matter abundance and the partial lifetime for two photon decay, while being consistent with constraints from domain wall formation and dark matter self-interactions. We show that all these features of the model are preserved in its natural embedding into a simple dark $U(1)$ gauge theory with a Higgs mechanism. The properties of the dark photon get determined in such a scenario. High precision cosmological measurements can potentially test these models, as there are residual effects from domain wall formation and non-negligible self-interactions of dark matter.