Search for the lepton flavour violating decay $$\mu ^+ \rightarrow \mathrm {e}^+ \gamma $$ μ + → e + γ with the full dataset of the MEG experiment

Abstract

The final results of the search for the lepton flavour violating decay Î1⁄4+→ e+Î3 based on the full dataset collected by the MEG experiment at the Paul Scherrer Institut in the period 2009–2013 and totalling 7.5 × 1014stopped muons on target are presented. No significant excess of events is observed in the dataset with respect to the expected background and a new upper limit on the branching ratio of this decay of B(Î1⁄4+→ e+Î3) < 4.2 × 10- 13(90 % confidence level) is established, which represents the most stringent limit on the existence of this decay to date.