Multi-component dark matter with magnetic moments for Fermi-LAT gamma-ray line

Abstract

We propose a model of multi-component dark matter with magnetic moments to explain the 130 GeV gamma-ray line hinted by the Fermi-LAT data. Specifically, we consider a U(1)_X dark sector which contains two vector-like fermions besides the related gauge and Higgs fields. A very heavy messenger scalar is further introduced to construct the Yukawa couplings of the dark fermions to the heavy [SU(2)]-singlet leptons in the SU(3)_c \times SU(2)_L \times SU(2)_R \times U(1)_{B-L} left-right symmetric models for universal seesaw. A heavier dark fermion with a very long lifetime can mostly decay into a lighter dark fermion and a photon at one-loop level. The dark fermions can serve as the dark matter particles benefited from their annihilations into the dark gauge and Higgs fields. In the presence of a U(1) kinetic mixing, the dark matter fermions can be verified by the ongoing and forthcoming dark matter direct detection experiments.