Year: 2026
Type: preprint
Abstract: We present a search for the lepton-flavor-violating decay $τ^{\pm}\toμ^{\pm}γ$ using a data sample that corresponds to an integrated luminosity of 428 fb$^{-1}$ recorded by the Belle II experiment at the SuperKEKB asymmetric-energy $e^{+}e^{-}$ collider. We employ a multivariate classifier to suppress the backgrounds from the Standard Model processes, and the signal extraction is performed using an extended maximum-likelihood fit. Since no significant excess over the expected background is observed, we set an upper limit on the branching fraction $\mathcal{B}(τ^{\pm}\toμ^{\pm}γ) < 9.5$$ (12.2)\times10^{-8}$ at the 90% (95%) confidence level, using the CL${_s}$ technique.
Source: arXiv (Cornell University)
Authors: Belle II Collaboration, Abumusabh, M., Adachi, I., Aggarwal, A., Ahmed, H., Ahn, Y., Aihara, H., Akdag, M., Akopov, N., Alghamdi, S., Alhakami, M., Aloisio, A., Althubiti, N., Amos, K., Angelsmark, M., Ky, N. Anh, Antonioli, C., Arai, K., Asner, D. M., Atmacan, H., Aushev, T., Aushev, V., Ayad, R., Babu, V., Bae, H., Baghel, N. K., Bahinipati, S., Bambade, P., Banerjee, Sw., Bansal, S., Barrett, M., Bartl, M., Baudot, J., Baur, A., Beaubien, A., Becherer, F., Becker, J., Bennett, J. V., Bernlochner, F. U., Bertacchi, V., Bertemes, M., Bertholet, E., Bessner, M., Bettarini, S., Bhardwaj, V., Bhuyan, B., Bianchi, F., Bilka, T., Biswas, A., Biswas, D., Bobrov, A., Bodrov, D., Bondar, A., Bonvicini, G., Borah, J., Boschetti, A., Bozek, A., Bračko, M., Branchini, P., Browder, T. E., Budano, A., Bussino, S., Callet, F., Campagna, Q., Campajola, M., Carminati, M., Casarosa, G., Cecchi, C., Chang, M. -C., Cheema, P., Chen, L., Cheon, B. G., Cheshta, C., Chetri, H., Chilikin, K., Chirapatpimol, K., Cho, H. -E., Cho, K., Cho, S. -J., Choi, S. -K., Choudhury, S., Chutia, S., Cochran, J., Colorado-Caicedo, J. A., Consigny, I., Corona, L., Ledesma, H. Crotte, Cuccuini, S., Cui, J. X., De La Cruz-Burelo, E., De La Motte, S. A., de Marino, G., De Nardo, G., De Pietro, G., de Sangro, R., Destefanis, M., Dey, S., Dhayal, R., Di Canto, A., Dingfelder, J., Doležal, Z., Jiménez, I. Dom\'ınguez, Dong, T. V., Dong, X., Dorigo, M., Dugic, K., Dujany, G., Ecker, P., Epifanov, D., Eppelt, J., Farkas, R., Feichtinger, P., Ferber, T., Fillinger, T., Finck, C., Finocchiaro, G., Forti, F., Frey, A., Fulsom, B. G., Gabrielli, A., Gagneja, P., Gale, A., Ganiev, E., Garcia-Hernandez, M., Garg, R., Garmash, A., Gärtner, L., Gaudino, G., Gaur, V., Gautam, V., Gaz, A., Gebeline, P., Gellrich, A., Ghevondyan, G., Ghosh, D., Ghumaryan, H., Giakoustidis, G., Giordano, R., Giri, A., Gironell, P. Gironella, Gobbo, B., Godang, R., Gogota, O., Gradl, W., Graziani, E., Greenwald, D., Guan, Y., Gudkova, K., Haide, I., Haigh, H., Han, Y., Hayasaka, K., Hayashii, H., Hazra, S., Hearty, C., Hedges, M. T., Heidelbach, A., Heine, G., de la Cruz, I. Heredia, Villanueva, M. Hernández, Higuchi, T., Hoek, M., Hohmann, M., Hoppe, R., Horak, P., Hou, X. T., Hsu, C. -L., Humair, T., Iijima, T., Inami, K., Ipsita, N., Ishikawa, A., Itoh, R., Iwasaki, M., Jackson, P., Jacobi, D., Jacobs, W. W., Jaffe, D. E., Jang, E. -J., Jia, S., Jin, Y., Johnson, A., Joo, K. K., Kakuno, H., Kaleta, M., Kang, K. H., Kang, S., Karyan, G., Kawasaki, T., Keil, F., Ketter, C., Khan, M., Kiesling, C., Kim, C., Kim, D. Y., Kim, H., Kim, J. -Y., Kim, K. -H., Kindo, H., Kinoshita, K., Kodyš, P., Koga, T., Kohani, S., Korobov, A., Korpar, S., Kovalenko, E., Kowalewski, R., Krein, M., Križan, P., Krokovny, P., Kuhr, T., Kulii, Y., Kumar, D., Kumar, J., Kumara, K., Kunigo, T., Kuzmin, A., Kwon, Y. -J., Lacaprara, S., Lam, T., Lanceri, L., Lange, J. S., Lau, T. S., Laurenza, M., Leboucher, R., Diberder, F. R. Le, Lee, H., Lee, M. J., Lemettais, C., Leo, P., Li, C., Li, H. -J., Li, L. K., Li, Q. M., Li, S. X., Li, W. Z., Li, Y., Li, Y. B., Liao, Y. P., Libby, J., Lin, J., Lin, S., Liptak, Z., Lisovskyi, V., Liu, C., Liu, G., Liu, M. H., Liu, Q. Y., Liu, Y., Liu, Z. Q., Liventsev, D., Longo, S., Lozar, A., Lueck, T., Lyu, C., Ma, J. L., Ma, Y., Maggiora, M., Maharana, S. P., Maiti, R., Mancinelli, G., Manfredi, R., Manoni, E., Mantovano, M., Marcantonio, D., Marcello, S., Marfoli, M., Marinas, C., Martellini, C., Martens, A., Martinov, T., Massaccesi, L., Masuda, M., Matsuda, T., Matsuoka, K., Matvienko, D., Maurya, S. K., Maushart, M., Mawas, F., McKenna, J. A., Gruberová, Z. Mediankin, Mehta, R., Meier, F., Meleshko, D., Merola, M., Miller, C., Mirra, M., Miyabayashi, K., Miyake, H., Mizuk, R., Mohanty, G. B., Moneta, S., de Carvalho, A. L. Moreira, Moser, H. -G., Mudgal, N., Muller, Th., Murakami, H., Mussa, R., Nakamura, I., Nakamura, K. R., Nakao, M., Nakazawa, Y., Naruki, M., Natkaniec, Z., Natochii, A., Nayak, M., Neu, M., Niiyama, M., Nishida, S., Nomaru, R., Novosel, A., Ogawa, S., Okubo, R., Ono, H., Onuki, Y., Ostrowski, I., Pakhlov, P., Pakhlova, G., Panta, A., Pardi, S., Parham, K., Park, J., Park, K., Park, S. -H., Passeri, A., Patra, S., Paul, S., Pedlar, T. K., Pestotnik, R., Piccolo, M., Piilonen, L. E., Podesta-Lerma, P. L. M., Podobnik, T., Polat, L., Prakash, A., Prasad, V., Praz, C., Prell, S., Prencipe, E., Prim, M. T., Privalov, S., Prudiiev, I., Purwar, H., Rados, P., Raiz, S., Ravindran, K., Rehman, J. U., Reif, M., Reiter, S., Remnev, M., Reuter, L., Herrmann, D. Ricalde, Ripp-Baudot, I., Rizzo, G., Robertson, S. H., Roney, J. M., Rostomyan, A., Rout, N., Russo, G., Saha, S., Salutari, L., Sanders, D. A., Sandilya, S., Santelj, L., Santos, C., Savinov, V., Scavino, B., Schmitz, J., Schneider, S., Schnepf, M., Schoenning, K., Schwanda, C., Seino, Y., Senyo, K., Serrano, J., Sevior, M. E., Sfienti, C., Shan, W., Shen, C. P., Shi, X. D., Shillington, T., Shimasaki, T., Shiu, J. -G., Shtol, D., Sibidanov, A., Simon, F., Singh, J. B., Skorupa, J., Sobie, R. J., Sobotzik, M., Soffer, A., Sokolov, A., Solovieva, E., Song, W., Spataro, S., Špenko, K., Spruck, B., Starič, M., Stavroulakis, P., Stefkova, S., Stroili, R., Strube, J., Sumihama, M., Sumisawa, K., Suwonjandee, N., Takahashi, M., Takizawa, M., Tamponi, U., Tanida, K., Tenchini, F., Testa, F., Thaller, A., Manh, T. Tien, Tittel, O., Tiwary, R., Torassa, E., Trabelsi, K., Trantou, F. F., Tsaklidis, I., Uchida, M., Ueda, I., Uglov, T., Unger, K., Unno, Y., Uno, K., Uno, S., Urquijo, P., Ushiroda, Y., Vahsen, S. E., van Tonder, R., Varvell, K. E., Veronesi, M., Vinokurova, A., Vismaya, V. S., Vitale, L., Vobbilisetti, V., Volk, R., Volpe, R., Wakai, M., Wallner, S., Wang, M. -Z., Warburton, A., Watanabe, M., Watanuki, S., Wessel, C., Won, E., Xu, X. P., Yabsley, B. D., Yamada, S., Yan, W., Yan, W., Yelton, J., Yi, K., Yin, J. H., Yoshihara, K., Yuan, C. Z., Yuan, J., Yuan, L., Yusa, Y., Zani, L., Zeng, F., Zeyrek, M., Zhang, B., Zhao, X., Zhilich, V., Zhou, J. S., Zhou, Q. D., Zhou, X. Y., Zhu, L., Žlebčík, R.
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, U.S. Department of Energy, Alexander von Humboldt-Stiftung, Univerzita Karlova v Praze, Grantová Agentura, Univerzita Karlova, University of Tabuk, Vietnam Academy of Science and Technology, Thailand Center of Excellence in Physics, Ministerio de Ciencia, Innovación y Universidades, National Research Foundation of Ukraine, European Commission, National Research Foundation, Deutsche Forschungsgemeinschaft, Agence Nationale de la Recherche, Ministry of Education, Culture, Sports, Science and Technology, National Natural Science Foundation of China, Ministerstvo Školství, Mládeže a Tělovýchovy, Grantová Agentura České Republiky, Austrian Science Fund, Korea Institute of Science and Technology, Korea Institute of Science and Technology Information, Ikerbasque, Basque Foundation for Science, Knut och Alice Wallenbergs Stiftelse, Max-Planck-Gesellschaft, Javna Agencija za Raziskovalno Dejavnost RS, Türkiye Bilimsel ve Teknolojik Araştırma Kurumu, Centre National de la Recherche Scientifique, Ministerio de Ciencia e Innovación, Forskningsrådet om Hälsa, Arbetsliv och Välfärd, Natural Science Foundation of Shandong Province, National Research University Higher School of Economics, Ministry of Education and Science of Ukraine, Ministry of Science and Higher Education of the Russian Federation, Istituto Nazionale di Fisica Nucleare, Bundesministerium für Bildung, Wissenschaft und Forschung, National Science and Technology Council, Alliance de recherche numérique du Canada, Korea Research Environment Open Network, HORIZON EUROPE Framework Programme, Natural Sciences and Engineering Research Council of Canada, Deutsches Elektronen-Synchrotron, Japan Society for the Promotion of Science, Akademi Sains Malaysia, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Agencia Estatal de Investigación, Institut National de Physique Nucléaire et de Physique des Particules
Awards: Effective Theories for Strong Interactions: Precision Tools to Meet Experiment, G1138632649, G1255754732, G1292439221, G1345453387, G1446753731, G1466111314, G1490384003, G1509888190, G1570660777, G1610934229, G1842629209, G1871341476, G190755355, G1913364353, G1935710221, G196419191, G1996771453, Search for New Physics by Global Analysis, G2029582843, G2076608, G2297643115, G2366539284, G241279073, Non-Leptonic Three-Body B Decays: Theory and Phenomenology, 地盤の耐震応答に関する基礎動力学的研究, RUI: Studies of Heavy Quarkonium Spectroscopy with Belle and Belle II, G2522279099, Search for physics beyond the Standard Model by studying lepton universality in B meson decays, G2668241615, G2677629327, G2678520069, PhenoAccess: Physiological Phenotyping of Brachypodium Accessions, A state-of-the-art pulsar survey to aid gravitational wave detection efforts through pulsar timing, Search for the Lepton Flavour Violating Decay Tau to Lepton + Gamma at the Belle II Experiment, G2975900969, G3046200081, Study of the structure for tau lepton flavor on Belle II, G326497735, A novel approach to meson or lepton decays to escaping particles, G3358600294, Experimental Nuclear Physics and Fundamental Interactions at Indiana University, G3480961101, G3550923839, G3561356256, G3614640056, G3810236772, G3812116678, G387734, キャビティショントラックチェンバー(超音波泡箱)の研究, G4014979219, G405252872, Testing Anomalies in B Meson Decays with Unprecedented Sensitivity: Exploration and Discovery, G4197854740, G4212894969, G4379173793, オルガノボラン(有機ほう素化合物)を用いる新しい有機合成に関する研究, G4396925471, G4511208782, Quark-hadron duality in B meson semileptonic decays, G466842207, G4671393316, G4673483196, Road toward the next standard model explored with muon precision physics, G4805177507, G4879365968, G5170186115, G5222023348, G5232368275, G5259210140, G5273183856, G5321654564, G5407126004, G545007060, Experimental Particle Physics, G5596435803, G5633341255, G5643255487, G5671187699, 赤芽球フェリチンの構造と機能に関する研究, G5765906131, G5831461947, G5838019525, G5954829367, G5958906545, G5988284195, G608581630, Collaborative Research: Dynamic Vegetation Feedback and Regional Climate Predictions in West Africa, G6242558066, G6507815512, Experimental test of lepton universality and improvements of particle identification at the Belle II experiment, Probing New Physics with Tau-Lepton, Charmingly Direct CP Violation, G6915156049, G698819318, G7032149085, G7079858060, G7080048889, G7095037090, G7145191310, StrangeCharm: Precision study of strange-charm baryons, G717256432, G7198535790, G7200992521, Fundamental aspects of new physics search in precision spectroscopy, G7586236497, G7692396955, Search for New Symmetry Violation in Leptons, Search for new physics by researching lepton universality with B and Y(2S) meson decays, Determination of -Vcb- from exclusive B decays at Belle II, REU Site: Grand Valley State University Summer Undergraduate Research Program in Mathematics, 体温調節機構の性分化メカニズムの解析, Exploration of the particle physics frontier at the Super B-factory and cultivation o f young researchers, Top quark mass and Yukawa coupling determinations at ILC, G8099446405, Measurement of Vcb in inclusive B decays at Belle II, G8140083606, Test of lepton universality in bottomonium decays, Precise measurement of muonium HFS for new physics search hunting, G8363112480, G8373305038, G8537746564, G8590477180, G872144517, G8908444087, G8920660035, Charmingly Radiative CP Violation, G9000118138, G9000132604, G9000229261, G9000236791, G9000354113, Investigation of the flavor anomaly problem by the world's highest luminosity accelerator experiment, G948983577
OpenAlex ID: W7204204891