Polarized gamma rays from dark matter annihilations

Abstract

In this paper, we explore the possibility of a linearly polarized gamma-ray signal from dark matter annihilations in the Galactic center. Considering neutral weakly interacting massive particles, a polarized gamma-ray signal can be realized by a two-component dark matter model of Majorana fermions with an anapole moment. We discuss the spin alignment of such dark matter fermions in the Galactic center and then estimate the intensity and the polarizability of the final-state electromagnetic radiation in the dark matter annihilations. For low-mass dark matter, the photon flux at sub-GeV energies may be polarized at a level detectable in current X-ray polarimeters. Depending on the mass ratio between the final-state fermion and DM, the degree of polarization at the mass threshold can reach $70\%$ or even higher, providing us with a new tool for probing the nature of dark matter in future gamma-ray polarization experiments.

19 pages, 7 figures. v2: version accepted by Physics Letters B

References in corpus (4)

• First results on low-mass dark matter from the CRESST-III experiment
• Performance measurement of HARPO: a Time Projection Chamber as a gamma-ray telescope and polarimeter
• Polarization of photons emitted by decaying dark matter
• On the Prospects for Detecting a Net Photon Circular Polarization Produced by Decaying Dark Matter

Cited by in corpus (4)

• Gamma Ray polarimetry; a new window for the non-thermal Universe
• Circularly Polarized Gamma Rays in Effective Dark Matter Theory
• HARPO, a gas TPC active target for high-performance $\gamma$-ray astronomy; demonstration of the polarimetry of MeV $\gamma$-rays converting to $e^{+}{e}^{-}$ pair
• Polarisation of high energy gamma-rays after scattering