Electroweak bremsstrahlung for wino-like Dark Matter annihilations

TL;DR

This paper calculates how electroweak bremsstrahlung affects wino-like Dark Matter annihilation, revealing that fermion channels can be as significant as bosonic ones, impacting particle flux predictions.

Contribution

It provides the first full tree-level calculation including electroweak bremsstrahlung for wino-like Dark Matter, showing the importance of fermion channels.

Findings

Fermion channels become as important as di-boson channels due to bremsstrahlung.

Electroweak bremsstrahlung lifts helicity suppression in Dark Matter annihilation.

Implications for Dark Matter indirect detection signals.

Abstract

If the Dark Matter is the neutral Majorana component of a multiplet which is charged under the electroweak interactions of the Standard Model, its main annihilation channel is into W+W-, while the annihilation into light fermions is helicity suppressed. As pointed out recently, the radiation of gauge bosons from the initial state of the annihilation lifts the suppression and opens up an s-wave contribution to the cross section. We perform the full tree-level calculation of Dark Matter annihilations, including electroweak bremsstrahlung, in the context of an explicit model corresponding to the supersymmetric wino. We find that the fermion channel can become as important as the di-boson one. This result has significant implications for the predictions of the fluxes of particles originating from Dark Matter annihilations.