Two-loop radiative seesaw with multicomponent dark matter explaining the possible gamma excess in the Higgs boson decay and at the Fermi LAT (1302.3936v2)

Abstract: A non-supersymmetric model of a two-loop radiative seesaw is proposed. The model contains, in addition to the standard model (SM) Higgs boson, an inert SU(2)L doublet scalar eta and two inert singlet scalars phi and chi. The lepton number is softly broken by a dimension-two operator, and the tree-level Dirac mass is forbidden by Z_2 x Z_2' (or D{2N}), which predicts the existence of two or three dark matter particles. The scalar sector is minimal; none of the scalar fields can be suppressed for the radiative seesaw mechanism to work. There are by-products: The SM Higgs boson decay into two gamma's is slightly enhanced by eta^+ (the charged component of eta) circulating in one-loop diagrams for h to gamma gamma. The 135 GeV gamma-ray line observed at the Fermi LAT can be also explained by the annihilation of chi dark matter. We employ a mechanism of temperature-dependent annihilation cross section to suppress the continuum gamma rays and the production of antiprotons. The explanation can survive even down to the XENON1T sensitivity limit.