Proton-Proton Bremsstrahlung at 65 MeV

Proton-proton bremsstrahlung cross sections were measured for final-state proton angles of (20°, 20°), (20°, 26°), (23°, 30°), (25°, 25°), (25°, 35°), (26°, 35°), (26.5°, 26.5°), and (30°, 30°). Differential cross sections as a function of $\gamma$-ray angle were extracted from four sets of data. A theoretical prediction of the (30°, 30°) angular distribution, averaged over the azimuthal acceptance of the counters, agrees well with the experimental result. Total cross sections were obtained at all pairs of angles mentioned and were used to estimate the coplanar cross sections. The coplanar cross sections agree with results of a model-independent soft-photon calculation. They are smaller than predictions made with either a hard-core potential or a momentum-dependent potential, but they favor the latter.