Search for dark matter signatures in the gamma-ray emission towards the Sun with the Fermi Large Area Telescope

TL;DR

This study searches for gamma-ray spectral features from dark matter annihilation near the Sun using 10 years of Fermi LAT data, setting constraints on dark matter properties and mediator decay lengths.

Contribution

It provides the first dedicated analysis of gamma-ray signatures from dark matter annihilation in the Sun with Fermi LAT, including constraints on scattering cross sections and mediator decay lengths.

Findings

No significant gamma-ray spectral features detected.

Set upper limits on dark matter-nucleon scattering cross sections.

Constraints depend on mediator decay length and dark matter mass.

Abstract

Dark matter particles from the Galactic halo can be gravitationally trapped in the solar core or in external orbits. The enhanced density of dark matter particles either in the solar core or in external orbits can result in the annihilation of these particles producing gamma rays via long-lived intermediate states or directly outside the Sun, respectively. These processes would yield characteristic features in the energy spectrum of the subsequent gamma rays, i.e., a box-like or line-like shaped feature, respectively. We have performed a dedicated analysis using a 10-years sample of gamma-ray events from the Sun collected by the Fermi Large Area Telescope searching for spectral features in the energy spectrum as a signature of dark matter annihilation. In the scenario of gamma-ray production via long-lived mediators we have also evaluated the dark matter-nucleon spin-dependent and spin-independent scattering cross section constraints from the flux limits in a dark matter mass range from 3 GeV/c$^2$ up to about 1.8 TeV/c$^2$. In the mass range up to about 150 GeV/c$^2$ the limits are in the range $10^{-46} - 10^{-45}$ cm$^{2}$ for the spin-dependent scattering and in the range $10^{-48} - 10^{-47}$ cm$^{2}$ for the spin-independent case. The range of variation depends on the decay length of the mediator.