We calculate the helicity amplitudes for the QED processes e+e-→γγγ, μ+μ-γ, and e+e-γ, in the limit of vanishing fermion masses. This is done by introducing explicit polarization vectors for the radiated photons. With the same technique, we also calculate these processes taking into account Z0 exchange. Finally, we present the unpolarized cross sections in which mass terms are retained to describe the radiation of photons in directions parallel to those of the fermions. © 1982.
Berends, F. A., Kleiss, R., De Causmaecker, P., Gastmans, R., Troost, W., & Wu, T. T. (1982). Multiple bremsstrahlung in gauge theories at high energies (II). Single bremsstrahlung. Nuclear Physics, Section B, 206(1), 61–89. https://doi.org/10.1016/0550-3213(82)90489-8