Asymmetric Dark Matter in Extended Exo-Higgs Scenarios

Abstract

The exo-Higgs model can accommodate a successful baryogenesis mechanism that closely mirrors electroweak baryogenesis in the Standard Model, but avoids its shortcomings. We extend the exo-Higgs model by the addition of a singlet complex scalar $χ$. In our model, $χ$ can be a viable asymmetric dark matter (ADM) candidate. We predict the mass of the ADM particle to be $m_χ\approx1.3\, \textrm{GeV}$. The leptophilic couplings of $χ$ can provide for efficient annihilation of the ADM pairs. We also discuss the LHC signals of our scenario, and in particular the production and decays of exo-leptons which would lead to "lepton pair plus missing energy" final states. Our model typically predicts potentially detectable gravitational waves originating from the assumed strong first order phase transition at a temperature of $\sim$ TeV. If the model is further extended to include new heavy vector-like fermions, {\it e.g.} from an ultraviolet extension, $χ$ couplings could explain the $\sim 3.5σ$ muon $g-2$ anomaly.