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 $\gamma\gamma$ and $\gamma Z$ line signals. The $CP$-violation phase will introduce an polarization asymmetry in the $\gamma\gamma$ final state. Then we study the direct detection prospect and discuss the complimentarity of these two search strategies. 
Fei Teng
hep-ph