A search for $μ^+\to e^+γ$ with the first dataset of the MEG II experiment

• DOI: 10.48550/arxiv.2310.12614
• Publication Date: 2023-01-01
• Authors: MEG II collaboration; K. Afanaciev; A. Baldini; S. Ban; V. A. Baranov; H. Benmansour; M. Biasotti; G. Boca; P. W. Cattaneo; G. Cavoto; F. Cei; M. Chiappini; G. Chiarello; A. Corvaglia; F. Cuna; G. Dal Maso; A. de Bari; M. De Gerone; Lorenzo Ferrari B...; M. Francesconi; L. Galli; G. Gallucci; F. Gatti; L. Gerritzen; F. Grancagnolo; E. G. Grandoni; M. Grassi; D.N. Grigoriev; M. Hildebrandt; K. Ieki; F.V. Ignatov; F. Ikeda; T. Iwamoto; С. Карпов; P. -R. Kettle; N. V. Khomutov; S. Kobayashi; A. Kolesnikov; N. P. Kravchuk; В. А. Крылов; N. A. Kuchinskiy; W. Kyle; T. Libeiro; V. L. Malyshev; A. Matsushita; M. Meucci; S. Mihara; W. Molzon; T. Mori; M. Nakao; D. Nicoló; H. Nishiguchi; A. Ochi; S. Ogawa; Rina Onda; W. Ootani; Atsushi Oya; D. Palo; M. Panareo; A. Papa; V. Pettinacci; A. S. Popov; F. Renga; S. Ritt; M. Rossella; A. Rozhdestvensky; P. Schwendimann; Kohei Shimada; G. Signorelli; Masato Takahashi; G. F. Tassielli; Kazuhiro Toyoda; Y. Uchiyama; M. Usami; A. Venturini; B. Vitali; C. Voena; Kensuke Yamamoto; K. Yanai; T. Yonemoto; Keisuke Yoshida; Yu. V. Yudin
• Keywords: Branching fraction

The MEG II experiment, based at the Paul Scherrer Institut in Switzerland, reports result of a search for decay $\mu^+\to e^+\gamma$ from data taken first physics run 2021. No excess events over expected background is observed, yielding an upper limit on branching ratio B($\mu^+\to e^+\gamma$) < $7.5 \times 10^{-13}$ (90% C.L.). combination this and obtained by gives $3.1 C.L.), which most stringent to date. A ten-fold larger sample being collected during years 2022-2023, data-taking will continue coming years.