Dark matter annihilation through a lepton-specific Higgs boson

Abstract

It was recently argued by Hooper and Goodenough [arXiv:1010.2752] that the excess gamma ray emission from within 1-2 degrees of the galactic center can be well-described by annihilation of ~8 GeV dark matter particles into tau pairs. I show that such a dark matter signal can be obtained naturally in the lepton-specific two-Higgs-doublet model extended by a stable singlet scalar dark matter candidate. The favored parameter region prefers a light Higgs state (below 200 GeV) with enhanced couplings to leptons and sizable invisible branching fraction. Part of the favored region leads to invisible decays of both of the CP-even neutral Higgs states.

Comments: 15 pages, no figures. V2: references added, fine-tuning discussion improved, submitted to PRD. V3: added Sec. 6 on direct detection prospects and associated refs, version accepted by PRD