3.5 keV X-ray Line Signal from Decay of Right-Handed Neutrino due to Transition Magnetic Moment

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.Comment: 11 Pages LaTeX, 2 Figures, 1 Tabl

Gamma Ray and Neutrino Flux from Annihilation of Neutralino Dark Matter at Galactic Halo Region in mAMSB Model

We consider the lightest supersymmetric particle (LSP), neutralino in minimal anomaly mediated supersymmetry breaking model (mAMSB) to be a possible candidate for weakly interacting massive particles (WIMP) or cold dark matter and investigate its direct and indirect detections. The theoretically allowed supersymmetric parametric space for such a model along with the recent bounds from LHC is constrained by the WMAP results for relic densities. The spin independent and spin dependent scattering cross sections for dark matter off nucleon are thus constrained from the WMAP results. They are found to be within the allowed regions of different ongoing direct detection experiments. The annihilation of such dark matter candidates at the galactic centre produce different standard model particles such as gamma rays, neutrinos etc. In this work, we calculate the possible fluxes of these $\gamma$-rays and neutrinos coming from the direction of the galactic centre (and its neighbourhood) at terrestrial or satellite borne detectors. The calcutated $\gamma$-ray flux is compared with the observational results of HESS experiment. The neutrino flux of different flavours from the galactic centre and at different locations away from the galactic centre produced by WIMP annihilation in this model are also obtained for four types of galactic dark matter halo profiles. The detection prospects of such $\nu_\mu$ coming from the direction of the galactic centre at the ANTARES under sea detector are discussed in terms of muon signal yield from these muon neutrinos. Both the gamma and neutrino signals are estimated for four different dark matter halo profiles.Comment: 34 pages LaTeX, 36 postscript figures; Text and figures modified, new figures added; version published in J. Phys.