What is μ-e Conversion ? μ μ-+(A,Z)→e-+(A,Z) muon decay in orbit Neutrino-less muon nuclear capture (=μ-e conversion) 1s state in a muonic atom nucleus μ − μ-+(A,Z)→e-+(A,Z) τ=0.88μs for Al Eμe ~ mμ-Bμ Bμ: binding energy of the 1s muonic atom muon decay in orbit μ- →e-νν nuclear muon capture Γ(μ-N→νN’) B(μ-N→e-N)= μ-+(A,Z) →νμ+(A,Z-1) Γ(μ-N→e-N)

Overview of the COMET Experiment Proton Beam pπμ 8GeV, ~7μA, 56kW The Muon Source Proton Target Pion Capture Muon Transport The Detector Muon Stopping Target Electron Transport Electron Detection 2x107 sec running Single event sensitivity 2.6 x 10-17 Current best limit 7x10-13 using Au target 90% C.L. upper limit 6.0 x 10-17

, G. Macharasivili , Y. Yudin , T. Hayashi

Schedule Engineering run in 2018