Gamma-Ray Lines in 15 Years of Fermi-LAT Data: New Constraints on Higgs Portal Dark Matter

TL;DR

This study analyzes 15 years of Fermi-LAT gamma-ray data to search for spectral lines indicative of dark matter annihilation, setting new constraints and exploring implications for Higgs portal dark matter models.

Contribution

It provides the first double-line analysis of gamma-ray signals from dark matter and constrains models explaining the Galactic Center Excess via Higgs-mediated annihilation.

Findings

No spectral lines detected in 15 years of data.

Strong constraints placed on dark matter annihilation to gamma-ray lines.

First double-line analysis for gamma-ray signals above 150 GeV.

Abstract

Monoenergetic $\gamma$-ray spectral lines are among the cleanest signatures of dark matter annihilation. We analyze 15 years of Fermi-LAT data, find no spectral lines, and place strong constraints on dark matter annihilation to monoenergetic $\gamma$-rays. Additionally, we produce the first double-line analysis of the coupled signals from $\gamma\gamma$ and $Z \gamma$ lines, which proves particularly powerful for dark matter masses above $\sim150$~GeV. From our constraints on a double-line feature, we investigate and constrain some minimal models where the Galactic Center Excess (GCE) can be fit by dark matter annihilation through the Higgs boson into Standard Model particles.