ON THE SOLUTION OF SOME RELATIVISTIC TWO BODY PROBLEM

Abstract

Bhabha scattering, that is the scattering of electrons and positrons, at energies of a few Me V has not attracted much attention in the past. While the agreement of the experimental Bhabha cross-section with quantum electrodynamics predictions was verified at the IO % level of accuracy [1], the excitation function has not been studied in detail due to the apparent lack of physical interest in this energy region. Recently, however, a strong motivation to thoroughly investigate Bhabha scattering at energies around 2 MeV has arisen from the anomalous positron lines observed at GSI (Dannstadt) [2]. The observation made by the spectroscopy of positrons emitted in the collision of heavy atoms, consists in the surprising detection [3] of monoenergetic positron lines at about 250-400 KeV energy superimposed on a continuum. Recent experiments revealed that these lines occur in all collision systems with 164<Z<188 with similar energies. Even more surprising, there is more than one e-lines per system [4] and most curious the e-lines are in coincidence with e - lines of the same energies [2]. More refined experiments designed to search for resonances in Bhabha scattering are presently being perfonned [5]. It is well known, magentic interaction in atomic and molecular physics are usually small. However, the situation is totally different at small (nuclear) distances and high particular energies, where magentic effects become strong and must be treated non-perturbatively [6].