Galactic center $γ$-ray excess in hidden sector DM models with dark gauge symmetries: local $Z_{3}$ symmetry as an example

Abstract: Hidden sector dark matter (DM) models with local dark gauge symmetry make a natural playground for the $\gamma$-ray excess from the galactic center (GC). In this paper, we first discuss in detail the GC $\gamma$-ray excess in scalar dark matter model with local $Z_{3}$ symmetry which was recently proposed by the present authors. Within this model, scalar DM with mass $30-70$GeV is allowed due to newly-opened (semi-)annihilation channels of DM pair into dark Higgs $\phi$ and/or dark photon $Z^{'}$ pair, and can fit the $\gamma$-ray spectrum from the GC. Then we argue that the GC gamma ray excess can be easily accommodated in hidden sector dark matter models where DM is stabilized by local gauge symmetries, due to the presence of dark Higgs (and also dark photon for Abelian dark gauge symmetry). As by-products, the Higgs portal interaction between the dark Higgs and the SM Higgs boson can improve the EW vacuum stability up to Planck scale, and enable the Higgs inflation scenario to have potentially large tensor-to-scalar ratio, $r\sim O(0.01 - 0.1)$.