Two-loop radiative seesaw mechanism with multicomponent dark matter explaining the possible γ excess in the Higgs boson decay and at the Fermi LAT

A nonsupersymmetric model of a two-loop radiative seesaw is proposed. The model contains, in addition to the standard model Higgs boson, an inert SU(2) sub(L) doublet scalar [eta] and two inert singlet scalars [varphi] and chi . The lepton number is softly broken by a dimension-two operator, and the tree-level mass of the left-handed neutrino is forbidden by Z sub(2) x Z' sub(2) (or D sub(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 standard model Higgs boson decay into two gamma 's is slightly enhanced by [eta] super(+) (the charged component of [eta]) circulating in one-loop diagrams for h arrow right 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.