  Electroweak corrections can play a crucial role in dark matter annihilation.
The emission of gauge bosons, in particular, leads to a secondary flux
consisting of all Standard Model particles, and may be described by electroweak
fragmentation functions. To assess the quality of the fragmentation function
approximation to electroweak radiation in dark matter annihilation, we have
calculated the flux of secondary particles from gauge-boson emission in models
with Majorana fermion and vector dark matter, respectively. For both models, we
have compared cross sections and energy spectra of positrons and antiprotons
after propagation through the galactic halo in the fragmentation function
approximation and in the full calculation. Fragmentation functions fail to
describe the particle fluxes in the case of Majorana fermion annihilation into
light fermions: the helicity suppression of the lowest-order cross section in
such models cannot be lifted by the leading logarithmic contributions included
in the fragmentation function approach. However, for other classes of models
like vector dark matter, where the lowest-order cross section is not
suppressed, electroweak fragmentation functions provide a simple,
model-independent and accurate description of secondary particle fluxes.
