BHABHA TO MOLLER CROSS-SECTION RATIOS IN THE ENERGY-RANGE 2.15-2.45-MEV

The cross sections for Bhabha and Moller scattering have been investigated in the energy range 2.1-2.4 MeV using monoenergetic positrons and electrons to search for hypothetical resonances superimposed to the continuum predicted by quantum electro dynamics. Bhabba-to-Mott, Moller-to-Mott and Moller-to-Bhabha cross section ratios were measured. The Bhabha-to-Mott ratios could be determined with statistical errors of typically 1% and remaining systematic errors not exceeding the statistical ones. No resonances in Bhabha scattering were observed. Limits for the intrinsic widths of hypothetical resonances are given. For the first time upper limits are deduced from our data for hypothetical resonances in the Moller scattering cross section in the MeV range. Additionally, Moller-to-Bhabha cross section ratios could be determined with good precision. A good agreement between the experimental and theoretical Moller-to-Bhabha ratios can be stated calling in question the recently predicted existence of series of narrow, unresolvable resonances in the Bhabha scattering cross section.