Electron Pair Production in the Field of the Proton and in the Field of the Electron by Photons of Energy from 10 Mev to 1 Bev

Abstract

A 24-in. diffusion cloud chamber filled with hydrogen and located in a magnetic field has been placed in the hardened bremsstrahlung beam of the Cornell synchrotron to study electron pair production in the proton field (P.F. pairs) and in the electron field (E.F. pairs). The E.F. pairs could be detected with an average efficiency of \ensuremath{\sim}85% and are about as abundant as the P.F. pairs. A total of 3065 pairs produced by photons with energy from 10 to 1040 Mev have been analyzed.The principal results are: (1) The recoil momentum distribution of the E.F. pairs is in good agreement with the distribution predicted by Suh and Bethe.(2) The cross section for E.F. pairs is consistent with that calculated by Wheeler and Lamb.(3) The distribution of the opening angle of P.F. and E.F. pairs is in general agreement with Borsellino's calculations, at large angles. However, the peak appears at smaller angles than predicted.