Local $Z_2$ scalar dark matter model confronting galactic ${\mathrm GeV}$-scale $\gamma$-ray

TL;DR

This paper introduces a local $Z_2$ scalar dark matter model with new particles that can explain the GeV gamma-ray excess from the Galactic Center through dark Higgs decay, aligning with relic density and detection constraints.

Contribution

The model incorporates a local $Z_2$ symmetry with additional dark sector fields, providing new annihilation channels and explaining gamma-ray excesses while satisfying experimental bounds.

Findings

Model successfully explains GeV gamma-ray excess from GC.

Dark Higgs decay accounts for gamma-ray signals.

Compatible with relic density and direct detection constraints.

Abstract

We present a scalar dark matter (DM) model where DM ($X_I$) is stabilized by a local $Z_2$ symmetry originating from a spontaneously broken local dark $U(1)_X$. Compared with the usual scalar DM with a global $Z_2$ symmetry, the local $Z_2$ model possesses three new extra fields, dark photon $Z^{'}$, dark Higgs $\phi$ and the excited partner of scalar DM ($X_R$), with the kinetic mixing and Higgs portal interactions dictated by local dark gauge invariance. The resulting model can accommodate thermal relic density of scalar DM without conflict with the invisible Higgs branching ratio and the bounds from DM direct detections, thanks to the newly opened channels, $X_I X_I \rightarrow Z^{'} Z^{'}, \phi\phi$. In particular, due to the new particles, the ${\rm GeV}$ scale $\gamma$-ray excess from the Galactic Center (GC) can be originated from the decay of dark Higgs boson which is produced in DM annihilations.