Gamma-ray signal from Dark Matter Annihilation mediated by mixing scalar mediators

We present here a study of the direct and indirect detection prospects of a generic dark matter simplified model, in which the Majorana dark matter interacts only with a Standard Model lepton and a pair of uncolored mixing scalar mediators. We first show that the mixing angle significantly changes the feature of internal bremsstrahlung, as well as the flux ratio of $γγ$ and $γZ$ line signals. The $CP$-violation phase will introduce an polarization asymmetry in the $γγ$ final state. Then we study the direct detection prospect and discuss the complimentarity of these two search strategies.