A simplified 2HDM with a scalar dark matter and the galactic center gamma-ray excess

Abstract

Due to the strong constraint from the LUX experiment, the scalar portal dark matter cannot generally explain a gamma-ray excess in the galactic center by the annihilation of dark matter to bb¯. With the motivation of eliminating the tension, we add a scalar dark matter to the aligned two-Higgs-doublet model, and focus on a simplified scenario, which has two main characteristics: (i) The heavy CP-even Higgs is the discovered 125 GeV Higgs boson, which has the same couplings to the gauge bosons and fermions as the SM Higgs. (ii) Only the light CP-even Higgs mediates the dark matter interactions with SM particles, which have no couplings to WW and ZZ, but have the independent couplings to the up-type quarks, down-type quarks and charged leptons. We find that the tension between 〈σv〉SS→bb¯ and the constraint from LUX induced by the scalar portal dark matter can go away for the isospin-violating dark matter–nucleon coupling with −1.0<fn/fp<0.7, and the constraints from the Higgs search experiments and the relic density of Planck are also satisfied.