This letter reports the result of the search for the decay μ+ → e+γ 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 2.2×10−13, 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(μ+ → e+γ) < 1.5 × 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.
Newlimit on the μ+ → e+γdecay with the MEG II experiment / Afanaciev, K.; Baldini, A. M.; Ban, S.; Benmansour, H.; Boca, G.; Cattaneo, P. W.; Cavoto, G.; Cei, F.; Chiappini, M.; Corvaglia, A.; Dal Maso, G.; De Bari, A.; De Gerone, M.; Barusso, L. F.; Francesconi, M.; Galli, L.; Gallucci, G.; Gatti, F.; Gerritzen, L.; Grancagnolo, F.; Grandoni, E. G.; Grassi, M.; Grigoriev, D. N.; Hildebrandt, M.; Ignatov, F.; Ikeda, F.; Iwamoto, T.; Karpov, S.; Kettle, P. -R.; Khomutov, N.; Kolesnikov, A.; Kravchuk, N.; Krylov, V.; Kuchinskiy, N.; Leonetti, F.; Li, W.; Malyshev, V.; Matsushita, A.; Mihara, S.; Moltzon, W.; Mori, T.; Nicol('o), D.; Nishiguchi, H.; Ochi, A.; Ogawa, H.; Ootani, W.; Oya, A.; Palo, D.; Panareo, M.; Papa, A.; Pasciuto, D.; Popov, A.; Renga, F.; Ritt, S.; Rossella, M.; Rozhdestvensky, A.; Scarpellini, S.; Signorelli, G.; Suzuki, H.; Takahashi, M.; Uchiyama, Y.; Umakoshi, R.; Venturini, A.; Vitali, B.; Voena, C.; Yamamoto, K.; Yokota, R.; Yonemoto, T.. - In: THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS. - ISSN 1434-6044. - 85:(2025), pp. 1-7. [10.48550/arXiv.2504.15711]
Newlimit on the μ+ → e+γdecay with the MEG II experiment
Cavoto, G.Membro del Collaboration Group
;Scarpellini, S.Membro del Collaboration Group
;Vitali, B.Membro del Collaboration Group
;Voena, C.Membro del Collaboration Group
;
2025
Abstract
This letter reports the result of the search for the decay μ+ → e+γ 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 2.2×10−13, 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(μ+ → e+γ) < 1.5 × 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.| File | Dimensione | Formato | |
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