Indirect Detection Imprint of a CP Violating Dark Sector

We introduce a simple scenario involving fermionic dark matter ($χ$) and singlet scalar mediators that may account for the Galactic Center GeV $γ$-ray excess while satisfying present direct detection constraints. CP-violation in the scalar potential leads to mixing between the Standard Model Higgs boson and the scalar singlet, resulting in three scalars $h_{1,2,3}$ of indefinite CP-transformation properties. This mixing enables s-wave $χ{\barχ}$ annihilation into di-scalar states, followed by decays into four fermion final states. The observed $γ$-ray spectrum can be fitted while respecting present direct detection bounds and Higgs boson properties for $m_χ = 60 \sim 80$ GeV, and $m_{h_3} \sim m_χ$. Searches for the Higgs exotic decay channel $h_1 \to h_3 h_3$ at the 14 TeV LHC should be able to further probe the parameter region favored by the $γ$-ray excess.

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