Dark Matter Identification with Gamma Rays from Dwarf Galaxies

TL;DR

This paper explores the potential of atmospheric Cherenkov telescopes to detect gamma-ray signals from dark matter annihilation in dwarf galaxies, aiming to identify dark matter properties and discriminate models.

Contribution

It demonstrates the feasibility of detecting FSR photons from dwarf galaxies and distinguishes between different dark matter annihilation models using the FSR spectrum.

Findings

Current and near-future ACTs can potentially detect FSR photons from dwarf galaxies.

FSR spectra can differentiate between two-lepton and four-lepton dark matter models.

Dark matter particle mass can be inferred from the FSR spectrum.

Abstract

If the positron fraction and combined electron-positron flux excesses recently observed by PAMELA, FERMI and HESS are due to dark matter annihilation into lepton-rich final states, the accompanying final state radiation (FSR) photons may be detected by ground-based atmospheric Cherenkov telescopes (ACTs). Satellite dwarf galaxies in the vicinity of the Milky Way are particularly promising targets for this search. We find that current and near-future ACTs have an excellent potential for discovering the FSR photons from dwarfs, although a discovery cannot be guaranteed due to large uncertainties in the fluxes resulting from lack of precise knowledge of dark matter distribution within the dwarfs. We also investigate the possibility of discriminating between different dark matter models based on the measured FSR photon spectrum. For typical parameters, we find that the ACTs can reliably distinguish models predicting dark matter annihilation into two-lepton final states from those favoring four-lepton final states (as in, for example, "axion portal" models). In addition, we find that the dark matter particle mass can also be determined from the FSR spectrum.