Antiproton constraints on dark matter annihilations from internal electroweak bremsstrahlung

TL;DR

This paper investigates constraints on dark matter annihilation into leptons and gauge bosons using cosmic antiproton data, providing bounds on astrophysical boost factors relevant for gamma-ray detection prospects.

Contribution

It introduces a method to constrain dark matter annihilation cross-sections and boost factors using antiproton measurements, including analysis of leptophilic models and neutralino benchmarks.

Findings

Constraints on annihilation cross-section into electrons and gauge bosons.

Upper limits on astrophysical boost factors in the Milky Way.

Implications for gamma-ray detection prospects with IACTs and CTA.

Abstract

If the dark matter particle is a Majorana fermion, annihilations into two fermions and one gauge boson could have, for some choices of the parameters of the model, a non-negligible cross-section. Using a toy model of leptophilic dark matter, we calculate the constraints on the annihilation cross-section into two electrons and one weak gauge boson from the PAMELA measurements of the cosmic antiproton-to-proton flux ratio. Furthermore, we calculate the maximal astrophysical boost factor allowed in the Milky Way under the assumption that the leptophilic dark matter particle is the dominant component of dark matter in our Universe. These constraints constitute very conservative estimates on the boost factor for more realistic models where the dark matter particle also couples to quarks and weak gauge bosons, such as the lightest neutralino which we also analyze for some concrete benchmark points. The limits on the astrophysical boost factors presented here could be used to evaluate the prospects to detect a gamma-ray signal from dark matter annihilations at currently operating IACTs as well as in the projected CTA.