Observation of an Excess of Events in E exp + E exp - Annihilations into Neutral Final-States Leading to Three Electromagnetic Showers at 10 GeV

摘要

During the UPSILON investigation at DORIS, we observed six events in the e exp + e exp - annihilation into three electromagnetic showers in a particular kinematical configuration where QED predicted 1.0 +- 0.4 events for the three-photon final-state. The excess events were not related to the UPSILON resonance. A cross-section of approximately 70 pb has been determined. (Atomindex citation 10:475672)