LFV: mu-e gamma experiment

The MEG experiment, which searches for a lepton flavor violating muon decay, μ⁺ →e⁺ γ, to explore new physics like supersymmetric grand unified theory, started physics run in 2008 at Paul Scherrer Institute in Switzerland, and was completed last year. Its innovative detector system enables orders of magnitude better sensitivity than previous experiments. We set a new 90% C.L. upper limit of 5.7 ×10^-13 on the branching ratio of the μ⁺ →e⁺ γ decay using physics data collected between 2009 and 2011, which is the most stringent limit on the existence of this decay to date. The analysis for 2012-2013 data is in progress, and the final results based on 2009-2013 will be published soon. Since the sensitivity improvement was limited by the accidental background, we have considered the MEG upgrade project (MEG II) which aims at a sensitivity enhancement of one order of magnitude compared with the current MEG experiment. The latest result of the MEG experiment as well as the upgrade plan of the MEG II experiment is described here.