New limit on the \mu+->e+\gamma decay with the MEG II experiment

K. Afanaciev; A. M. Baldini; S. Ban; H. Benmansour; G. Boca; P. W. Cattaneo; G. Cavoto; F. Cei; M. Chiappini; A. Corvaglia; G. Dal Maso; A. De Bari; M. De Gerone; L. Ferrari Barusso; M. Francesconi; L. Galli; G. Gallucci; F. Gatti; L. Gerritzen; F. Grancagnolo; E. G. Grandoni; M. Grassi; D. N. Grigoriev; M. Hildebrandt; F. Ignatov; F. Ikeda; T. Iwamoto; S. Karpov; P. -R. Kettle; N. Khomutov; A. Kolesnikov; N. Kravchuk; V. Krylov; N. Kuchinskiy; F. Leonetti; W. Li; V. Malyshev; A. Matsushita; S. Mihara; W. Moltzon; Toshinori Mori; D. Nicolo'; H. Nishiguchi; A. Ochi; H. Ogawa; W. Ootani; A. Oya; D. Palo; M. Panareo; A. Papa

New limit on the \mu+->e+\gamma decay with the MEG II experiment

High Energy Physics - Experiment 2025-07-31 v2

Authors: K. Afanaciev , A. M. Baldini , S. Ban , H. Benmansour , G. Boca , P. W. Cattaneo , G. Cavoto , F. Cei , M. Chiappini , A. Corvaglia , G. Dal Maso , A. De Bari , M. De Gerone , L. Ferrari Barusso , M. Francesconi , L. Galli , G. Gallucci , F. Gatti , L. Gerritzen , F. Grancagnolo , E. G. Grandoni , M. Grassi , D. N. Grigoriev , M. Hildebrandt , F. Ignatov , F. Ikeda , T. Iwamoto , S. Karpov , P. -R. Kettle , N. Khomutov , A. Kolesnikov , N. Kravchuk , V. Krylov , N. Kuchinskiy , F. Leonetti , W. Li , V. Malyshev , A. Matsushita , S. Mihara , W. Moltzon , Toshinori Mori , D. Nicolo' , H. Nishiguchi , A. Ochi , H. Ogawa , W. Ootani , A. Oya , D. Palo , M. Panareo , A. Papa , D. Pasciuto , A. Popov , F. Renga , S. Ritt , M. Rossella , A. Rozhdestvensky , S. Scarpellini , G. Signorelli , H. Suzuki , M. Takahashi , Y. Uchiyama , R. Umakoshi , A. Venturini , B. Vitali , C. Voena , K. Yamamoto , R. Yokota , T. Yonemoto

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Abstract

This letter reports the result of the search for the decay \mu+->e+\gamma undertaken at the Paul Scherrer Institut in Switzerland with the MEG II experiment using the data collected in the 2021- 2022 physics runs. The sensitivity of this search is 2.2x10-13, a factor of 2.4 better than that of the full MEG dataset and obtained in a data taking period of about one fourth that of MEG, thanks to the superior performances of the new detector. The result is consistent with the expected background, yielding an upper limit on the branching ratio of B(\mu+->e+\gamma)<1.5 x 10-13 (90 % C.L.). Additional improvements are expected with the data collected during the years 2023-2024. The data-taking will continue in the coming years.

Keywords

muon decay branching ratio MEG II experiment lepton flavor violation sensitivity upper limit

Cite

@article{arxiv.2504.15711,
  title  = {New limit on the \mu+->e+\gamma decay with the MEG II experiment},
  author = {K. Afanaciev and A. M. Baldini and S. Ban and H. Benmansour and G. Boca and P. W. Cattaneo and G. Cavoto and F. Cei and M. Chiappini and A. Corvaglia and G. Dal Maso and A. De Bari and M. De Gerone and L. Ferrari Barusso and M. Francesconi and L. Galli and G. Gallucci and F. Gatti and L. Gerritzen and F. Grancagnolo and E. G. Grandoni and M. Grassi and D. N. Grigoriev and M. Hildebrandt and F. Ignatov and F. Ikeda and T. Iwamoto and S. Karpov and P. -R. Kettle and N. Khomutov and A. Kolesnikov and N. Kravchuk and V. Krylov and N. Kuchinskiy and F. Leonetti and W. Li and V. Malyshev and A. Matsushita and S. Mihara and W. Moltzon and Toshinori Mori and D. Nicolo' and H. Nishiguchi and A. Ochi and H. Ogawa and W. Ootani and A. Oya and D. Palo and M. Panareo and A. Papa and D. Pasciuto and A. Popov and F. Renga and S. Ritt and M. Rossella and A. Rozhdestvensky and S. Scarpellini and G. Signorelli and H. Suzuki and M. Takahashi and Y. Uchiyama and R. Umakoshi and A. Venturini and B. Vitali and C. Voena and K. Yamamoto and R. Yokota and T. Yonemoto},
  journal= {arXiv preprint arXiv:2504.15711},
  year   = {2025}
}

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6 pages, 4 figures

New limit on the \mu+->e+\gamma decay with the MEG II experiment

Abstract

Keywords

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