Model-independent dark matter annihilation bound from the diffuse gamma ray flux

TL;DR

This paper establishes a model-independent upper limit on dark matter annihilation cross sections using diffuse gamma-ray flux data, highlighting the significance of electroweak bremsstrahlung effects even when DM couples only to neutrinos.

Contribution

It demonstrates that gamma-ray observations can set competitive bounds on dark matter annihilation, independent of specific models, due to electroweak processes.

Findings

Gamma-ray flux constrains TeV-scale dark matter annihilation cross sections.

Electroweak bremsstrahlung induces electromagnetic signals even with neutrino-only couplings.

Future gamma-ray data from GLAST will tighten these bounds.

Abstract

An upper limit on the total annihilation cross section of dark matter (DM) has recently been derived from the observed atmospheric neutrino background. We show that comparable bounds are obtained for DM masses around the TeV scale by observations of the diffuse gamma-ray flux by EGRET, because electroweak bremsstrahlung leads to non-negligible electromagnetic branching ratios, even if DM particles only couple to neutrinos at tree level. A better mapping and the partial resolution of the diffuse gamma-ray background into astrophysical sources by the GLAST satellite will improve this bound in the near future.