Thermally produced scalar singlet as leptonphilic dark matter

Abstract

This work proposes a simple extension of the Standard Model where a scalar singlet and a leptonphilic scalar doublet exist. The scalar singlet could act as thermally produced dark matter. It annihilates into leptons through $s$-channel and benefit from the Breit--Winger resonance, so current thermally averaged cross-section are greatly enhanced. The constraints from the isotropic diffuse $\gamma$-ray background and correct dark matter relic abundance are analyzed. We find that the enhanced cross-section could fit the needed cross-section to explain the cosmic electron/positron excess.