A search for $$\upmu ^+ \rightarrow \textrm{e}^+ \upgamma $$ with the first dataset of the MEG II experiment

作者：K. Afanaciev, A. Baldini, S. Ban, Vladimir 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, 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, K. Ieki, F.V. Ignatov, F. Ikeda, T. Iwamoto, S.V. Karpov, P.-R. Kettle, N. V. Khomutov, S. Kobayashi, A. Kolesnikov, N. 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. Nicolò, H. Nishiguchi, A. Ochi, S. Ogawa, Rina Onda, W. Ootani, A. Oya, D. Palo, M. Panareo, A. Papa, V. Pettinacci, A. Yu. 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 · 发表于：The European Physical Journal C · 年份：2024 · DOI：10.1140/epjc/s10052-024-12416-2 · 被引用次数：49 · 研究领域：Particle physics theoretical and experimental studies、Dark Matter and Cosmic Phenomena、Quantum Chromodynamics and Particle Interactions

Abstract The MEG II experiment, based at the Paul Scherrer Institut in Switzerland, reports the result of a search for the decay $$\upmu ^+ \rightarrow {\textrm{e}}^+ \upgamma $$ 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 $${\mathcal {B}} (\upmu ^+ \rightarrow {\textrm{e}}^+ \upgamma ) < 7.5 \times 10^{-13}$$ B ( μ + → e + γ ) < 7.5 × 10 - 13 (90% CL). The combination of this result and the limit obtained by MEG gives $${\mathcal {B}} (\upmu ^+ \rightarrow {\textrm{e}}^+ \upgamma ) < 3.1 \times 10^{-13}$$ 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.