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Register a new userDark Matter Macroscopic Pearls, 3.55 keV X-ray line, How big ?
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Authors
Holger Bech Nielsen
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We study the 3.55 keV X-ray suspected to arise from dark matter in our model of dark matter consisting of a bubble of a new phase of the vacuum, the surface tension of which keeps ordinary matter under high pressure inside the bubble. We consider t
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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.
Recent data from Reticulum II (RetII) require the energy range of the FermiLAT $gamma$-excess to be $sim$ $2-10$ GeV. We adjust our unified nonthermal Dark Matter (DM) model to accommodate this. We have two extra scalars beyond the Standard Model to also explain 3.55 keV X-ray line. Now the mass of the heavier of them has to be increased to lie around 250 GeV, while that of the lighter one remains at 7.1 keV. This requires a new seed mechanism for the $gamma$-excess and new Boltzmann equations for the generation of the DM relic density. All concerned data for RetII and the X-ray line can now be fitted well and consistency with other indirect limits attained.
A two component model of nonthermal dark matter is formulated to simultaneously explain the Fermi-LAT results indicating a $gamma$-ray excess observed from our Galactic Centre in the 1-3 GeV energy range and the detection of an X-ray line at 3.55 keV from extragalactic sources. Two additional Standard Model singlet scalar fields $S_2$ and $S_3$ are introduced. These fields couple among themselves and with the Standard Model Higgs doublet $H$. The interaction terms among the scalar fields, namely $H$, $S_2$ and $S_3$, are constrained by the application of a discrete $mathbb{Z}_2times mathbb{Z}^prime_2$ symmetry which breaks softly to a remnant $mathbb{Z}^{prime prime}_2$ symmetry. This residual discrete symmetry is then spontaneously broken through an MeV order vacuum expectation value $u$ of the singlet scalar field $S_3$. The resultant physical scalar spectrum has the Standard Model like Higgs as $chi_{{}_{{}_1}}$ with $M_{chi_{{}_{{}_1}}}sim 125$ GeV, a moderately heavy scalar $chi_{{}_{{}_2}}$ with $50 ,,{rm GeV} leq M_{chi_{{}_{{}_2}}}leq 80,,{rm GeV}$ and a light $chi_{{}_{{}_3}}$ with $M_{chi_{{}_{{}_3}}} sim 7$ keV. There is only tiny mixing between $chi_{{}_{{}_1}}$ and $chi_{{}_{{}_2}}$ as well as between $chi_{{}_{{}_1}}$ and $chi_{{}_{{}_3}}$. The lack of importance of domain wall formation in the present scenario from the spontaneous breaking of the discrete symmetry ${mathbb{Z}_2^{primeprime}}$, provided $uleq 10$ MeV, is pointed out. We find that our proposed two component dark matter model is able to explain successfully both the above mentioned phenomena $-$ the Fermi-LAT observed $gamma$-ray excess (from the $chi_{{}_{{}_2}} rightarrow {rm b} bar{rm b}$ decay mode) and the observation of the X-ray line (from the decay channel $chi_{{}_{{}_3}}rightarrowgamma gamma$) by the XMM-Newton observatory.
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.
Galaxy clusters can efficiently convert axion-like particles (ALPs) to photons. We propose that the recently claimed detection of a 3.55--3.57 keV line in the stacked spectra of a large number of galaxy clusters and the Andromeda galaxy may originate from the decay of either a scalar or fermionic $7.1$ keV dark matter species into an axion-like particle (ALP) of mass $m_{a} lesssim 6cdot 10^{-11}~{rm eV}$, which subsequently converts to a photon in the cluster magnetic field. In contrast to models in which the photon line arises directly from dark matter decay or annihilation, this can explain the anomalous line strength in the Perseus cluster. As axion-photon conversion scales as $B^2$ and cool core clusters have high central magnetic fields, this model can also explains the observed peaking of the line emission in the cool cores of the Perseus, Ophiuchus and Centaurus clusters, as opposed to the much larger dark matter halos. We describe distinctive predictions of this scenario for future observations.
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