Search for Features in the Cosmic-Ray Electron and Positron spectrum measured by the Fermi Large Area Telescope

TL;DR

This study uses Fermi LAT data to search for spectral features in cosmic-ray electrons and positrons, aiming to detect signs of dark matter or astrophysical sources, but finds no such features and sets constraints on dark matter properties.

Contribution

First search for delta-like spectral features in cosmic-ray electrons and positrons with Fermi LAT, providing new limits on dark matter annihilation cross sections.

Findings

No delta-like spectral features detected.

Constraints set on dark matter annihilation cross section.

Limits extend up to 1.7 TeV mass, excluding thermal cross section for DM below 150 GeV.

Abstract

The Large Area Telescope onboard the Fermi Gamma-ray Space Telescope has collected the largest ever sample of high-energy cosmic-ray electron and positron events. Possible features in their energy spectrum could be a signature of the presence of nearby astrophysical sources, or of more exotic sources, such as annihilation or decay of dark matter (DM) particles in the Galaxy. In this paper for the first time we search for a delta-like line feature in the cosmic-ray electron and positron spectrum. We also search for a possible feature originating from DM particles annihilating into electron-positron pairs. Both searches yield negative results, but we are able to set constraints on the line intensity and on the velocity-averaged DM annihilation cross section. Our limits extend up to DM masses of 1.7 $TeV/c^2$, and exclude the thermal value of the annihilation cross-section for DM lighter than 150 $GeV/c^2$.