Vector Higgs-portal dark matter and Fermi-LAT gamma ray line

Abstract

We propose a renormalizable model for vector dark matter with extra U(1) gauge symmetry, which is broken by the vacuum expectation value of a complex singlet scalar. When the singlet scalar has a quartic coupling to a heavy charged scalar, the resonance effect enhances the annihilation cross section of vector dark matter into two photons such that a Fermi gamma ray line at about 130 GeV is obtained. In the presence of a tiny mixing between the singlet scalar and the Standard Model Higgs doublet, the relic density is determined dominantly by WW/ZZ and two-photon channels near the resonance pole of the singlet scalar. We also show that various phenomenological bounds coming from the Higgs-to-diphoton decay rate, precision data, and collider searches for the charged scalar and vacuum stability are satisfied in the model.