Updated Search for Spectral Lines from Galactic Dark Matter Interactions with Pass 8 Data from the Fermi Large Area Telescope

TL;DR

This paper reports a comprehensive search for gamma-ray spectral lines from dark matter interactions in the Milky Way using 5.8 years of Pass 8 Fermi LAT data, finding no significant signals but re-evaluating previous tentative detections.

Contribution

It introduces an improved analysis with extended data and modified observing strategy, enhancing sensitivity to potential dark matter spectral lines.

Findings

No significant spectral line detections in the analyzed data.

Reassessment of the 133 GeV line claim with new Pass 8 data.

Enhanced sensitivity due to increased exposure and analysis techniques.

Abstract

Dark matter in the Milky Way may annihilate directly into gamma rays, producing a monoenergetic spectral line. Therefore, detecting such a signature would be strong evidence for dark matter annihilation or decay. We search for spectral lines in the Fermi Large Area Telescope observations of the Milky Way halo in the energy range 200 MeV to 500 GeV using analysis methods from our most recent line searches. The main improvements relative to previous works are our use of 5.8 years of data reprocessed with the Pass 8 event-level analysis and the additional data resulting from the modified observing strategy designed to increase exposure of the Galactic center region. We searched in five sky regions selected to optimize sensitivity to different theoretically-motivated dark matter scenarios and find no significant detections. In addition to presenting the results from our search for lines, we also investigate the previously reported tentative detection of a line at 133 GeV using the new Pass 8 data.