Proton-proton bremsstrahlung cross-sections including the kinematical singularity

Integrated cross-section data for proton-proton bremsstrahlung including the points with the phase-space singularity, which occurs close to the maximum non-coplanarity angle, are presented. A numerical integration of theoretical cross-sections is performed over the non-coplanarity angle to integrate out this singularity. Furthermore, a comparison is made between measured cross-sections and predictions of two soft-photon models. All features observed for the data far from the singularity, including the overestimation of the cross-section by $ \approx$ 30% by the theoretical calculations, emerge as well for the data close to and including the singularity.