Electroweak Bremsstrahlung in Dark Matter Annihilation

TL;DR

This paper calculates electroweak bremsstrahlung processes in dark matter annihilation, revealing that radiative corrections produce detectable photons, thus tightening constraints on dark matter interaction rates.

Contribution

It provides explicit calculations of electroweak bremsstrahlung branching ratios in dark matter annihilation, highlighting their role in generating observable electromagnetic signals.

Findings

Electroweak bremsstrahlung produces photons that can be detected.

Radiative corrections lead to additional constraints on dark matter annihilation.

Calculations are applicable to both dark matter annihilation and decay.

Abstract

A conservative upper bound on the total dark matter (DM) annihilation rate can be obtained by constraining the appearance rate of the annihilation products which are hardest to detect. The production of neutrinos, via the process $\chi \chi \to \bar\nu \nu $, has thus been used to set a strong general bound on the dark matter annihilation rate. However, Standard Model radiative corrections to this process will inevitably produce photons which may be easier to detect. We present an explicit calculation of the branching ratios for the electroweak bremsstrahlung processes $\chi \chi \to \bar\nu \nu Z$ and $\chi \chi \to \bar\nu e W$. These modes inevitably lead to electromagnetic showers and further constraints on the DM annihilation cross-section. In addition to annihilation, our calculations are also applicable to the case of dark matter decay.