Experimental study of the reactions e(+)e(-)→e(+)e(-) and e(+)e(-)→γγ at 29 GeV

Abstract

This paper reports measurements of the differential cross sections for the reactions e(+)e(-)→e(+)e(-) (Bhabha scattering) and e(+)e(-)→γγ (γ-pair production). The reactions are studied at a center-of-mass energy of 29 GeV and in the polar-angular region ‖costheta‖<0.55. A direct cross-section comparison between these two reactions provides a sensitive test of the predictions of quantum electrodynamics (QED) to order α(3). When the ratio of γ-pair to Bhabha experimental cross sections, integrated over ‖costheta‖<0.55, is divided by the same ratio predicted from α(3) QED theory, the result is 1.007±0.009±0.008. The 95%-confidence limits on the QED-cutoff parameters are Λ+>154 GeV and Λ->220 GeV for Bhabha scattering, and Λ+>59 GeV and Λ->59 GeV for γ-pair production.