An experiment has been performed to search for the muon-and electron-number non-conserving decay µ + → e + γ. The upper limit for the branching ratio is found to be Γ(µ−11 with 90% confidence.13.35.Bv; 11.30.Er; 23.40.Bw

The MEGA experiment, which searched for the muon-and electron-number violating decay ϩ →e ϩ ␥, is described. The spectrometer system, the calibrations, the data taking procedures, the data analysis, and the sensitivity of the experiment are discussed. The most stringent upper limit on the branching ratio, B( ϩ →e ϩ ␥)Ͻ1.2ϫ10 Ϫ11 with 90% confidence, is derived from a likelihood analysis.