| Summary: | Positron excess observed by PAMELA, Fermi and AMS02 may be due to dark matter (DM) pair annihilation or decay dominantly into muons. In this paper, we consider a scenario with thermal fermionic DM (χ) with mass ∼O(1–2) TeV decaying into a dark Higgs (ϕ) and an active neutrino (νa) instead of the SM Higgs boson and νa. We first present a renormalizable model for this scenario with local dark U(1)X gauge symmetry, in which the DM χ can be thermalized by Higgs portal and the gauge kinetic mixing. Assuming the dark Higgs (ϕ) mass is in the range 2mμ<mϕ<2mπ0, the positron excess can be fit if a proper background model is used, without conflict with constraints from antiproton and gamma-ray fluxes or direct detection experiments. Also, having such a light dark Higgs, the self-interaction of DM can be enhanced to some extent, and three puzzles in the CDM paradigm can be somewhat relaxed.
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