Electron-Electron Scattering at 15.7 Mev

The differential scattering cross section for electron-electron scattering has been measured at relativistic energies. A focused beam of 15.7-Mev monokinetic electrons from the 22-Mev betatron was scattered by 1- and 2-mil Nylon foils in a 20-inch scattering chamber. The incident current was collected by a faraday cage after it had passed through the scattering foil and was measured by a vibrating reed electrometer. The scattered beam was defined by gold-lined slits at a known angle to the incident beam. The number of scattered electrons in a given momentum interval chosen by a magnetic analyzer was counted by a Geiger counter.Energy analysis of the scattered electrons made it possible to separate the nuclear scattering events from the electron scattering events. The energy of the scattered electrons was measured as a function of the scattering angle and was found to be in agreement with the laws of relativistic mechanics within an experimental accuracy of 0.4 percent.For the electron-electron collisions the relative scattering cross sections agree with the M{}ller formula. For the electron-nuclear collisions they agree with the relativistic Mott theory (Born approximation) corrected for the radiative losses as calculated by Schwinger (3 to 8 percent). The experimental consistency of the cross sections was about 4 percent.The absolute differential scattering cross sections for the electron-nuclear scattering were measured at angles between 10^∘{} and 43^∘{}. The average of the absolute values was 2 percent lower than theory. This is probably due to systematic errors in the solid angle, and in the collection and counting efficiencies.The absolute differential scattering cross sections for electron-electron scattering were measured at the same set of angles, which correspond to the angular interval of 70^∘{} to 150^∘{} in the center-of-mass system. The average of these absolute cross sections was 7 percent lower than theory predicts. The bulk of the 5 percent additional departure from theory may be due to a systematic error in the measurement of the momentum interval defined by the counter.