Generic dark matter signature for gamma-ray telescopes

TL;DR

This paper identifies a unique gamma-ray signature from dark matter annihilation or decay under specific conditions, and analyzes existing data to predict a potential future detection at atmospheric Cherenkov telescopes.

Contribution

It introduces a characteristic gamma-ray spectral signature for certain dark matter models and connects this to current observational data, predicting a detectable signal at ACTs.

Findings

A specific gamma-ray spectral shape is predicted for certain dark matter scenarios.

Analysis of Fermi LAT, PAMELA, and HESS data shows hints supporting this signature.

Future observations at atmospheric Cherenkov telescopes could confirm the signal.

Abstract

We describe a characteristic signature of dark matter (DM) annihilation or decay into gamma-rays. We show that if the total angular momentum of the initial DM particle(s) vanishes, and helicity suppression operates to prevent annihilation/decay into light fermion pairs, then the amplitude for the dominant 3-body final state f^+f^-\gamma has a unique form dictated by gauge invariance. This amplitude and the corresponding energy spectra hold for annihilation of DM Majorana fermions or self-conjugate scalars, and for decay of DM scalars, thus encompassing a variety of possibilities. Within this scenario, we analyze Fermi LAT, PAMELA and HESS data, and predict a hint in future Fermi gamma-ray data that portends a striking signal at atmospheric Cherenkov telescopes (ACTs).