KeV channeling effects in the Mott scattering of electrons and positrons

High-energy scattering experiments mandate a point-like charge on the electron. However, the spectroscopic properties of the electron suggest an overall Compton-sized geometry. Adopting the model of a Compton-sized electron or positron that has a equatorial point charge, we use detailed computer calculations of classical Coulomb scattering off atomic nuclei to delineate the boundaries of a narrow energy window, in the KeV range, in which finite-size effects should be observable. Some experimental evidence for these finite-size effects can be found in the published literature.1. This work was performed under the auspices of the U. S. Department of Energy by the Lawrence Livermore National Laboratory under contract No. W-7405-ENG-48.2. The impact parameters shown in Fig. 1 were obtained by numerical integration of point-particle trajectories, with relativistic effects and nuclear screening included.3. When rotational and recoil effects are set equal to zero, the calculated large-positron elastic differential cross sections are accurately point-like at all incident energies.4. The calculations shown here required more than 10,000 hours of computer time on a network of seven Sun SPARC 1 and SPARC 2 computers.