Electron-Electron Scattering at 6.1 Mev

Abstract

The absolute differential cross section for the scattering of 6.1-Mev electrons by the electrons in a beryllium foil has been measured at 90 degrees and 109 degrees in the center-of-mass system. Electrons from a linear accelerator were first magnetically analyzed and then collimated to form the incident beam. Electron-electron scattering events were detected by end-window Geiger counters connected in coincidence. The counter with the defining aperture was connected in coincidence (1) with a counter at the conjugate scattering-angle, lying in the plane determined by the incident beam and the scattering direction to the defining counter; and (2), with another counter at the conjugate angle, but lying outside this plane, thus counting only accidental coincidences. The number of $e\ensuremath{-}e$ coincidences was then given by the difference between (1) and (2), with appreciable corrections arising from asymmetry in the background and from dead-time losses. These corrections required measurements of single and coincidence count rates with the scatterer in and out of the beam.The result at 109 degrees was 4.4 percent lower than that predicted by the M\o{}ller theory, with a standard deviation based on the number of counts recorded of \ifmmode\pm\else\textpm\fi{}6 percent. At 90 degrees the expected standard deviation was \ifmmode\pm\else\textpm\fi{}2 percent, and here the experimental result was 8 percent below the theoretical. The latter result suggests the possibility that the M\o{}ller theory overestimates the cross section. However, consideration of the effects produced by radiative collisions, and of possible systematic errors in the experiment, leads to the conclusion that the experimental result is not incompatible with the M\o{}ller theory.