Indirect Detection Imprint of a CP Violating Dark Sector

Abstract

We introduce a simple scenario involving fermionic dark matter ($\chi$) and singlet scalar mediators that may account for the Galactic Center GeV $\gamma$-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 $\chi \bar{\chi }$ annihilation into di-scalar states, followed by decays into four fermion final states. The observed $\gamma$-ray spectrum can be fitted while respecting present direct detection bounds and Higgs boson properties for $m_{\chi }=60\sim 80$ GeV, and $m_{h_3}\sim m_{\chi }$. 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 $\gamma$-ray excess.

Comments: 18 pages, 13 figures, 1 table