부산대학교 도서관

The MEG II experiment, based at the Paul Scherrer Institut in Switzerland, reports the result of a search for the decay μ + → e + γ from data taken in the first physics run in 2021. No excess of events over the expected background is observed, yielding an upper limit on the branching ratio of B (μ + → e + γ) < 7.5 × 10 - 13 (90% CL). The combination of this result and the limit obtained by MEG gives B (μ + → e + γ) < 3.1 × 10 - 13 (90% CL), which is the most stringent limit to date. A ten-fold larger sample of data is being collected during the years 2022–2023, and data-taking will continue in the coming years. [ABSTRACT FROM AUTHOR]