Extended Higgs-portal dark matter and the Fermi-LAT Galactic Center Excess

TL;DR

This paper proposes an extended Higgs-portal dark matter model with an additional scalar that explains the Fermi-LAT Galactic Center Excess while satisfying experimental constraints.

Contribution

The paper introduces an economical extended Higgs-portal model with a second scalar, providing a good fit to the GCE data and consistent relic density, improving upon the standard SHP.

Findings

The extended model fits GCE data with p-value ~0.6-0.7.

Dark matter mass around 130 GeV explains the excess.

Model remains consistent with relic density and other constraints.

Abstract

We show that the Galactic Center Excess (GCE) emission, as recently updated by the Fermi-LAT Collaboration, could be explained by the sum of Fermi-bubbles-like emission plus dark matter (DM) annihilation, in the context of a scalar-singlet Higgs portal scenario (SHP). In fact, the standard SHP, where the DM particle, $S$, only has renormalizable interactions with the Higgs, is non-operational due to strong constraints, specially from DM direct detection limits. Thus we consider a most economical extension, called ESHP (for extended SHP), which simply consists in the addition of a second (heavier) scalar singlet in the dark sector. The second scalar can be integrated-out, leaving a standard SHP plus a dimension-6 operator. Essentially, this model has only two relevant parameters (the DM mass and the coupling of the dim-6 operator). DM annihilation occurs mainly into two Higgs bosons, $SS\rightarrow hh$. We demonstrate that, despite its economy, the ESHP model provides excellent fits to the GCE (with p-value $\sim 0.6-0.7$) for very reasonable values of the parameters, in particular $m_S \simeq 130$ GeV. This is achieved without conflicting with other observables and keeping the $S-$particle relic density at the accepted value for the DM content in the universe.