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

TL;DR

This paper proposes a non-supersymmetric two-loop radiative seesaw model with multicomponent dark matter, explaining gamma-ray excesses in Higgs decay and Fermi LAT observations, while predicting minimal scalar sector and enhanced Higgs to gamma gamma decay.

Contribution

It introduces a novel two-loop radiative seesaw model with multiple dark matter particles and explains gamma-ray excesses with temperature-dependent annihilation mechanisms.

Findings

Enhanced Higgs to gamma gamma decay rate due to charged scalar loops.

Explanation of Fermi LAT 135 GeV gamma-ray line via dark matter annihilation.

Model remains consistent with XENON1T dark matter detection limits.

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.