Dark Matter Annihilation Signals: The Importance of Radiative Corrections

TL;DR

This paper emphasizes the significance of internal bremsstrahlung as a spectral signature in gamma-ray signals from dark matter annihilation, which could surpass line signals and aid in identifying dark matter properties.

Contribution

It highlights the importance of radiative corrections, especially internal bremsstrahlung, in dark matter indirect detection and their potential to distinguish dark matter candidates.

Findings

IB dominates high-energy gamma-ray spectra from DM annihilation

IB signatures can differentiate between DM models

Radiative corrections may explain positron excesses

Abstract

Being able to safely distinguish astrophysical from potential dark matter (DM) annihilation signals is of utmost importance for indirect DM searches. To this end, one has to rely on distinctive -- and unique -- spectral signatures to look for. Internal bremsstrahlung (IB), unavoidable in the presence of charged annihilation products, provides such a signature. In fact, as it generically dominates the gamma-ray spectrum expected from DM annihilations, at high energies, it may well turn out to be more important for indirect DM searches than the traditionally looked-for line signals. As illustrated in some detail, the observation of IB signatures would even allow to distinguish between different DM candidates or to constrain significantly the parameter space of, e.g., neutralino DM. The gamma-ray contributions reported here are therefore of great interest for the already launched Fermi/GLAST satellite and the upcoming new generation of Air Cherenkov Telescope systems like CTA -- which are most sensitive at the high energies where these effects are particularly important. Finally, radiative corrections may even significantly alter the positron spectrum from DM annihilations; an intriguing positron excess recently found by the PAMELA satellite might turn out to be an indication of the peculiar spectral signature expected in that case.