Electroweak Bremsstrahlung in Dark Matter Annihilation

Understand

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 $\chi \chi \to \bar\nu e W$.