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

TL;DR

This paper proposes a simplified two-Higgs-doublet model with scalar dark matter to explain the galactic center gamma-ray excess, addressing experimental constraints and introducing isospin-violating interactions.

Contribution

It introduces a minimal scalar dark matter extension to the aligned 2HDM, allowing for gamma-ray excess explanation while satisfying experimental bounds.

Findings

Scalar dark matter can explain gamma-ray excess with isospin violation.

Constraints from LUX and Higgs searches are satisfied in the model.

The model remains consistent with relic density measurements.

Abstract

Due to the strong constrain from the LUX experiment, the scalar portal dark matter can not generally explain a gamma-ray excess in the galactic center by the annihilation of dark matter into $b\bar{b}$. 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 has no couplings to $WW$ and $ZZ$, but the independent couplings to the up-type quarks, down-type quarks and charged leptons. We find that the tension between $<\sigma v>_{SS\to b\bar{b}}$ and the constraint from LUX induced by the scalar portal dark matter can go away for the isospin-violating dark matter-nucleon coupling with $-1.0< f^n/f^p<0.7$, and the constraints from the Higgs search experiments and the relic density of Planck are also satisfied.