Gamma-Ray Lines from Radiative Dark Matter Decay

TL;DR

This paper investigates the radiative decay of leptophilic dark matter particles into gamma-ray lines, providing theoretical decay rate calculations and discussing observational prospects with Cherenkov telescopes like CTA.

Contribution

It introduces a model-independent calculation of radiative decay rates for scalar and fermionic dark matter, linking cosmic-ray anomalies to potential gamma-ray line signals.

Findings

Radiative decay rates are computed for leptophilic dark matter.

A potential gamma-ray line at a few TeV could indicate dark matter decay.

Observational prospects with CTA are discussed.

Abstract

The decay of dark matter particles which are coupled predominantly to charged leptons has been proposed as a possible origin of excess high-energy positrons and electrons observed by cosmic-ray telescopes PAMELA and Fermi LAT. Even though the dark matter itself is electrically neutral, the tree-level decay of dark matter into charged lepton pairs will generically induce radiative two-body decays of dark matter at the quantum level. Using an effective theory of leptophilic dark matter decay, we calculate the rates of radiative two-body decays for scalar and fermionic dark matter particles. Due to the absence of astrophysical sources of monochromatic gamma rays, the observation of a line in the diffuse gamma-ray spectrum would constitute a strong indication of a particle physics origin of these photons. We estimate the intensity of the gamma-ray line that may be present in the energy range of a few TeV if the dark matter decay interpretation of the leptonic cosmic-ray anomalies is correct and comment on observational prospects of present and future Imaging Cherenkov Telescopes, in particular the CTA.