Proton-Proton Bremsstrahlung Calculations

The pole contribution to the proton-proton bremsstrahlung cross section is shown to give the cross section exactly to order $K^0$, where $K$ is the photon momentum, in the gauge in which the photon polarization ${\epsilon }^{\mu }$ has ${\epsilon }^0=0\mathrm{}$ in the center-of-mass system. To this order there are no off-energy-shell (OES) contributions. Calculations are presented using the pole contribution only to test the sensitivity of the cross section to the OES effects, which come from higher-order terms in $K$. The quasiphases which describe the OES behavior of the $\mathrm{pp}$ scattering amplitude are parametrized, and the sensitivity of the cross section is studied in terms of this parametrization. The results are compared with calculations based on the Hamada-Johnston potential and with the results of other authors. It is found that for favorable geometries above 50 MeV the variation in this cross section for different OES behavior is sufficient to be measured. This sensitivity comes largely from terms in the magnetic interaction and the tensor and spin-orbit part of the $\mathrm{pp}$ interaction.