Dark Matter Interpretation of the Fermi-LAT Observation Toward the Galactic Center

TL;DR

This paper investigates gamma-ray excess near the Galactic Center observed by Fermi-LAT, interpreting it as potential dark matter annihilation signals, and constrains dark matter particle properties within an effective field theory framework.

Contribution

It characterizes the gamma-ray excess as dark matter annihilation using effective field theory, constraining interaction types and particle properties based on Fermi-LAT data.

Findings

Excess favors dark matter particles with mass 50-190 GeV.

Annihilation cross sections are constrained between 1E-26 and 4E-25 cm^3/s.

Pseudo-scalar interactions are consistent with direct detection limits.

Abstract

The center of the Milky Way is predicted to be the brightest region of gamma-rays generated by self-annihilating dark matter particles. Excess emission about the Galactic center above predictions made for standard astrophysical processes has been observed in gamma-ray data collected by the Fermi Large Area Telescope. It is well described by the square of an NFW dark matter density distribution. Although other interpretations for the excess are plausible, the possibility that it arises from annihilating dark matter is valid. In this paper, we characterize the excess emission as annihilating dark matter in the framework of an effective field theory. We consider the possibility that the annihilation process is mediated by either pseudo-scalar or vector interactions and constrain the coupling strength of these interactions by fitting to the Fermi Large Area Telescope data for energies 1-100 GeV in the 15 x 15 degree region about the Galactic center using self-consistently derived interstellar emission models and point source lists for the region. The excess persists and its spectral characteristics favor a dark matter particle with a mass in the range approximately from 50 to 190 (10 to 90) GeV and annihilation cross section approximately from 1E-26 to 4E-25 (6E-27 to 2E-25) cm^3/s for pseudo-scalar (vector) interactions. We map these intervals into the corresponding WIMP-neutron scattering cross sections and find that the allowed range lies well below current and projected direct detection constraints for pseudo-scalar interactions, but are typically ruled out for vector interactions.