Low energy e⁺e^- scattering

Electron-positron scattering provides a model-independent test for the existence of neutral particles coupling to the e⁺e^- field. The authors review the effects of possible particle resonances X⁰ in the energy range between threshold and a few MeV on electron-positron scattering. The presentation focuses on theoretical aspects, but results of precision measurements of Bhabha scattering and e⁺e^- annihilation in flight are also briefly surveyed.