Search for lepton-flavor-violating τ− → μ−μ+μ− decays at Belle II
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Published:2024-09-11
Issue:9
Volume:2024
Page:
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ISSN:1029-8479
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Container-title:Journal of High Energy Physics
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language:en
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Short-container-title:J. High Energ. Phys.
Author:
, Adachi I.ORCID, Aggarwal L.ORCID, Aihara H.ORCID, Akopov N.ORCID, Aloisio A.ORCID, Althubiti N.ORCID, Anh Ky N.ORCID, Asner D. M.ORCID, Atmacan H.ORCID, Aushev V.ORCID, Aversano M.ORCID, Ayad R.ORCID, Babu V.ORCID, Bae H.ORCID, Bahinipati S.ORCID, Bambade P.ORCID, Banerjee Sw.ORCID, Bansal S.ORCID, Barrett M.ORCID, Baudot J.ORCID, Baur A.ORCID, Beaubien A.ORCID, Becherer F.ORCID, Becker J.ORCID, Bennett J. V.ORCID, Bernlochner F. U.ORCID, Bertacchi V.ORCID, Bertemes M.ORCID, Bertholet E.ORCID, Bessner M.ORCID, Bettarini S.ORCID, Bianchi F.ORCID, Bierwirth L.ORCID, Bilka T.ORCID, Biswas D.ORCID, Bobrov A.ORCID, Bodrov D.ORCID, Bolz A.ORCID, Borah J.ORCID, Boschetti A.ORCID, Bozek A.ORCID, Bračko M.ORCID, Branchini P.ORCID, Browder T. E.ORCID, Budano A.ORCID, Bussino S.ORCID, Campagna Q.ORCID, Campajola M.ORCID, Cao L.ORCID, Casarosa G.ORCID, Cecchi C.ORCID, Cerasoli J.ORCID, Chang M.-C.ORCID, Chang P.ORCID, Cheaib R.ORCID, Cheema P.ORCID, Chen C.ORCID, Cheon B. G.ORCID, Chilikin K.ORCID, Chirapatpimol K.ORCID, Cho H.-E.ORCID, Cho K.ORCID, Cho S.-J.ORCID, Choi S.-K.ORCID, Choudhury S.ORCID, Cochran J.ORCID, Corona L.ORCID, Cui J. X.ORCID, Das S.ORCID, Dattola F.ORCID, De La Cruz-Burelo E.ORCID, De La Motte S. A.ORCID, De Nardo G.ORCID, De Nuccio M.ORCID, De Pietro G.ORCID, de Sangro R.ORCID, Destefanis M.ORCID, Dey S.ORCID, Dhamija R.ORCID, Di Canto A.ORCID, Di Capua F.ORCID, Dingfelder J.ORCID, Doležal Z.ORCID, Domínguez Jiménez I.ORCID, Dong T. V.ORCID, Dorigo M.ORCID, Dorner D.ORCID, Dort K.ORCID, Dossett D.ORCID, Dreyer S.ORCID, Dubey S.ORCID, Dugic K.ORCID, Dujany G.ORCID, Ecker P.ORCID, Eliachevitch M.ORCID, Feichtinger P.ORCID, Ferber T.ORCID, Ferlewicz D.ORCID, Fillinger T.ORCID, Finck C.ORCID, Finocchiaro G.ORCID, Fodor A.ORCID, Forti F.ORCID, Frey A.ORCID, Fulsom B. G.ORCID, Gabrielli A.ORCID, Ganiev E.ORCID, Garcia-Hernandez M.ORCID, Garg R.ORCID, Gaudino G.ORCID, Gaur V.ORCID, Gaz A.ORCID, Gellrich A.ORCID, Ghevondyan G.ORCID, Ghosh D.ORCID, Ghumaryan H.ORCID, Giakoustidis G.ORCID, Giordano R.ORCID, Giri A.ORCID, Glazov A.ORCID, Gobbo B.ORCID, Godang R.ORCID, Gogota O.ORCID, Goldenzweig P.ORCID, Gradl W.ORCID, Grammatico T.ORCID, Granderath S.ORCID, Graziani E.ORCID, Greenwald D.ORCID, Gruberová Z.ORCID, Gu T.ORCID, Guan Y.ORCID, Gudkova K.ORCID, Halder S.ORCID, Han Y.ORCID, Hara T.ORCID, Harris C.ORCID, Hayasaka K.ORCID, Hayashii H.ORCID, Hazra S.ORCID, Hearty C.ORCID, Hedges M. T.ORCID, Heidelbach A.ORCID, Heredia de la Cruz I.ORCID, Hernández Villanueva M.ORCID, Higuchi T.ORCID, Hoek M.ORCID, Hohmann M.ORCID, Horak P.ORCID, Hsu C.-L.ORCID, Humair T.ORCID, Iijima T.ORCID, Inami K.ORCID, Inguglia G.ORCID, Ipsita N.ORCID, Ishikawa A.ORCID, Itoh R.ORCID, Iwasaki M.ORCID, Jacobs W. W.ORCID, Jaffe D. E.ORCID, Jang E.-J.ORCID, Ji Q. P.ORCID, Jia S.ORCID, Jin Y.ORCID, Junkerkalefeld H.ORCID, Kaleta M.ORCID, Kalita D.ORCID, Kaliyar A. B.ORCID, Kandra J.ORCID, Kang K. H.ORCID, Kang S.ORCID, Karyan G.ORCID, Kawasaki T.ORCID, Keil F.ORCID, Kiesling C.ORCID, Kim C.-H.ORCID, Kim D. Y.ORCID, Kim K.-H.ORCID, Kim Y.-K.ORCID, Kindo H.ORCID, Kinoshita K.ORCID, Kodyš P.ORCID, Koga T.ORCID, Kohani S.ORCID, Kojima K.ORCID, Konno T.ORCID, Korobov A.ORCID, Korpar S.ORCID, Kovalenko E.ORCID, Kowalewski R.ORCID, Kraetzschmar T. M. G.ORCID, Križan P.ORCID, Krokovny P.ORCID, Kuhr T.ORCID, Kulii Y.ORCID, Kumar J.ORCID, Kumar M.ORCID, Kumar R.ORCID, Kumara K.ORCID, Kunigo T.ORCID, Kuzmin A.ORCID, Kwon Y.-J.ORCID, Lacaprara S.ORCID, Lalwani K.ORCID, Lam T.ORCID, Lanceri L.ORCID, Lange J. S.ORCID, Laurenza M.ORCID, Lautenbach K.ORCID, Leboucher R.ORCID, Le Diberder F. R.ORCID, Lee M. J.ORCID, Leo P.ORCID, Lemettais C.ORCID, Levit D.ORCID, Lewis P. M.ORCID, Li L. K.ORCID, Li S. X.ORCID, Li Y.ORCID, Li Y. B.ORCID, Libby J.ORCID, Liu M. H.ORCID, Liu Q. Y.ORCID, Liu Y.ORCID, Liu Z. Q.ORCID, Liventsev D.ORCID, Longo S.ORCID, Lueck T.ORCID, Lyu C.ORCID, Ma Y.ORCID, Maggiora M.ORCID, Maharana S. P.ORCID, Maiti R.ORCID, Maity S.ORCID, Mancinelli G.ORCID, Manfredi R.ORCID, Manoni E.ORCID, Mantovano M.ORCID, Marcantonio D.ORCID, Marcello S.ORCID, Marinas C.ORCID, Martellini C.ORCID, Martini A.ORCID, Martinov T.ORCID, Massaccesi L.ORCID, Masuda M.ORCID, Matsuoka K.ORCID, Matvienko D.ORCID, Maurya S. K.ORCID, McKenna J. A.ORCID, Mehta R.ORCID, Meier F.ORCID, Merola M.ORCID, Metzner F.ORCID, Miller C.ORCID, Mirra M.ORCID, Mitra S.ORCID, Miyabayashi K.ORCID, Mohanty G. B.ORCID, Mondal S.ORCID, Moneta S.ORCID, Moser H.-G.ORCID, Mrvar M.ORCID, Mussa R.ORCID, Nakamura I.ORCID, Nakamura K. R.ORCID, Nakao M.ORCID, Nakazawa Y.ORCID, Narimani Charan A.ORCID, Naruki M.ORCID, Narwal D.ORCID, Natkaniec Z.ORCID, Natochii A.ORCID, Nayak L.ORCID, Nayak M.ORCID, Nazaryan G.ORCID, Neu M.ORCID, Niebuhr C.ORCID, Ninkovic J.ORCID, Nishida S.ORCID, Ogawa S.ORCID, Onishchuk Y.ORCID, Ono H.ORCID, Otani F.ORCID, Pakhlov P.ORCID, Pakhlova G.ORCID, Pardi S.ORCID, Parham K.ORCID, Park H.ORCID, Park J.ORCID, Park S.-H.ORCID, Paschen B.ORCID, Passeri A.ORCID, Patra S.ORCID, Paul S.ORCID, Pedlar T. K.ORCID, Peschke R.ORCID, Pestotnik R.ORCID, Piccolo M.ORCID, Piilonen L. E.ORCID, Pinna Angioni G.ORCID, Podesta-Lerma P. L. M.ORCID, Podobnik T.ORCID, Pokharel S.ORCID, Praz C.ORCID, Prell S.ORCID, Prencipe E.ORCID, Prim M. T.ORCID, Prudiev I.ORCID, Purwar H.ORCID, Rados P.ORCID, Raeuber G.ORCID, Raiz S.ORCID, Rauls N.ORCID, Reif M.ORCID, Reiter S.ORCID, Reuter L.ORCID, Ripp-Baudot I.ORCID, Rizzo G.ORCID, Robertson S. H.ORCID, Roehrken M.ORCID, Roney J. M.ORCID, Rostomyan A.ORCID, Rout N.ORCID, Russo G.ORCID, Sanders D. A.ORCID, Sandilya S.ORCID, Santelj L.ORCID, Sato Y.ORCID, Savinov V.ORCID, Scavino B.ORCID, Schneider S.ORCID, Schwanda C.ORCID, Schwickardi M.ORCID, Seino Y.ORCID, Selce A.ORCID, Senyo K.ORCID, Serrano J.ORCID, Sevior M. E.ORCID, Sfienti C.ORCID, Shan W.ORCID, Sharma C.ORCID, Shen C. P.ORCID, Shi X. D.ORCID, Shillington T.ORCID, Shimasaki T.ORCID, Shiu J.-G.ORCID, Shtol D.ORCID, Sibidanov A.ORCID, Simon F.ORCID, Singh J. B.ORCID, Skorupa J.ORCID, Smith K.ORCID, Sobie R. J.ORCID, Sobotzik M.ORCID, Soffer A.ORCID, Sokolov A.ORCID, Solovieva E.ORCID, Spataro S.ORCID, Spruck B.ORCID, Starič M.ORCID, Stavroulakis P.ORCID, Stefkova S.ORCID, Stroili R.ORCID, Sue Y.ORCID, Sumihama M.ORCID, Sumisawa K.ORCID, Sutcliffe W.ORCID, Suwonjandee N.ORCID, Svidras H.ORCID, Takahashi M.ORCID, Takizawa M.ORCID, Tamponi U.ORCID, Tanaka S.ORCID, Tanida K.ORCID, Tenchini F.ORCID, Thaller A.ORCID, Tittel O.ORCID, Tiwary R.ORCID, Tonelli D.ORCID, Torassa E.ORCID, Trabelsi K.ORCID, Tsaklidis I.ORCID, Ueda I.ORCID, Uglov T.ORCID, Unger K.ORCID, Unno Y.ORCID, Uno K.ORCID, Uno S.ORCID, Urquijo P.ORCID, Ushiroda Y.ORCID, Vahsen S. E.ORCID, van Tonder R.ORCID, Varvell K. E.ORCID, Veronesi M.ORCID, Vinokurova A.ORCID, Vismaya V. S.ORCID, Vitale L.ORCID, Vobbilisetti V.ORCID, Volpe R.ORCID, Vossen A.ORCID, Wach B.ORCID, Wakai M.ORCID, Wallner S.ORCID, Wang E.ORCID, Wang M.-Z.ORCID, Wang X. L.ORCID, Wang Z.ORCID, Warburton A.ORCID, Watanabe M.ORCID, Watanuki S.ORCID, Wessel C.ORCID, Xu X. P.ORCID, Yabsley B. D.ORCID, Yamada S.ORCID, Yan W.ORCID, Yang S. B.ORCID, Yelton J.ORCID, Yin J. H.ORCID, Yook Y. M.ORCID, Yoshihara K.ORCID, Yuan C. Z.ORCID, Zani L.ORCID, Zeng F.ORCID, Zhang B.ORCID, Zhang Y.ORCID, Zhilich V.ORCID, Zhou Q. D.ORCID, Zhou X. Y.ORCID, Zhukova V. I.ORCID, Žlebčík R.ORCID
Abstract
Abstract
We present the result of a search for the charged-lepton-flavor violating decay τ− → μ−μ+μ− using a 424 fb−1 sample of data recorded by the Belle II experiment at the SuperKEKB e+e− collider. The selection of e+e− → τ+τ− events is based on an inclusive reconstruction of the non-signal tau decay, and on a boosted decision tree to suppress background. We observe one signal candidate, which is compatible with the expectation from background processes. We set a 90% confidence level upper limit of 1.9 × 10−8 on the branching fraction of the τ−→ μ−μ+μ− decay, which is the most stringent bound to date.
Publisher
Springer Science and Business Media LLC
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