New Constraint on the Existence of the μ+→e+γ Decay

The analysis of a combined data set, totaling $3.6ifmmodetimeselsetexttimesfi{}{10}^{14}$ stopped muons on target, in the search for the lepton flavor violating decay ${ensuremath{mu}}^{+}ensuremath{rightarrow}{e}^{+}ensuremath{gamma}$ is presented. The data collected by the MEG experiment at the Paul Scherrer Institut show no excess of events compared to background expectations and yield a new upper limit on the branching ratio of this decay of $5.7ifmmodetimeselsetexttimesfi{}{10}^{ensuremath{-}13}$ (90% confidence level). This represents a four times more stringent limit than the previous world best limit set by MEG.