Two Lines or Not Two Lines? That is the Question of Gamma Ray Spectra

TL;DR

This paper explores the theoretical expectation of multiple gamma-ray lines from dark matter annihilation and analyzes Fermi-LAT data to determine if observed features are consistent with single or multiple lines, aiding dark matter detection strategies.

Contribution

It introduces the expectation of multiple gamma-ray lines from dark matter annihilation within an effective field theory framework and applies this to interpret Fermi-LAT data.

Findings

Data is consistent with a single gamma-gamma line.

Data is also consistent with a single gamma-Z line.

Data could indicate both gamma-gamma and gamma-Z lines.

Abstract

Lines in the spectrum of cosmic gamma rays are considered one of the more robust signatures of dark matter annihilation. We consider such processes from an effective field theory vantage, and find that generically, two or more lines are expected, providing an interesting feature that can be exploited for searches and reveal details about the underlying theory of dark matter. Using the 130 GeV feature recently reported in the Fermi-LAT data as an example, we analyze the energy spectrum in the multi-line context and find the data to be consistent with a single $\gamma\gamma$ line, a single $\gamma Z$ line or both a $\gamma \gamma$ and a $\gamma Z$ line.