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Search for $B^{0} \to τ^{\pm} ℓ^{\mp}$ ( $ℓ = e$ , $μ$ ) with a hadronic tagging method at Belle

H. Atmacan ⁷, A. J. Schwartz⁷, K. Kinoshita⁷, I. Adachi^19,15, K. Adamczyk⁶⁴, H. Aihara⁸⁸, S. Al Said^81,40, D. M. Asner³, V. Aulchenko^4,67 et al. (The Belle Collaboration)

V. Aulchenko^4,67, T. Aushev²⁰, R. Ayad⁸¹, V. Babu⁸, S. Bahinipati²⁴, M. Bauer³⁷, P. Behera²⁷, K. Belous³¹, J. Bennett⁵⁵, F. Bernlochner², M. Bessner¹⁸, V. Bhardwaj²³, B. Bhuyan²⁵, T. Bilka⁵, J. Biswal³⁶, A. Bobrov^4,67, A. Bozek⁶⁴, M. Bračko^52,36, P. Branchini³³, T. E. Browder¹⁸, A. Budano³³, M. Campajola^32,59, L. Cao², D. Červenkov⁵, M.-C. Chang¹⁰, P. Chang⁶³, V. Chekelian⁵³, A. Chen⁶¹, B. G. Cheon¹⁷, K. Chilikin⁴⁷, H. E. Cho¹⁷, K. Cho⁴², S.-K. Choi¹⁶, Y. Choi⁷⁹, S. Choudhury²⁶, D. Cinabro⁹², S. Cunliffe⁸, S. Das⁵¹, N. Dash²⁷, G. De Nardo^32,59, G. De Pietro³³, R. Dhamija²⁶, F. Di Capua^32,59, J. Dingfelder², Z. Doležal⁵, T. V. Dong¹¹, S. Dubey¹⁸, D. Epifanov^4,67, T. Ferber⁸, D. Ferlewicz⁵⁴, A. Frey¹⁴, B. G. Fulsom⁶⁹, R. Garg⁷⁰, V. Gaur⁹¹, N. Gabyshev^4,67, A. Garmash^4,67, A. Giri²⁶, P. Goldenzweig³⁷, E. Graziani³³, D. Greenwald⁸³, T. Gu⁷², Y. Guan⁷, K. Gudkova^4,67, C. Hadjivasiliou⁶⁹, S. Halder⁸², T. Hara^19,15, O. Hartbrich¹⁸, K. Hayasaka⁶⁶, H. Hayashii⁶⁰, W.-S. Hou⁶³, C.-L. Hsu⁸⁰, K. Inami⁵⁸, G. Inguglia³⁰, A. Ishikawa^19,15, R. Itoh^19,15, M. Iwasaki⁶⁸, Y. Iwasaki¹⁹, W. W. Jacobs²⁸, S. Jia¹¹, Y. Jin⁸⁸, K. K. Joo⁶, A. B. Kaliyar⁸², K. H. Kang⁴⁵, Y. Kato⁵⁸, T. Kawasaki⁴¹, C. Kiesling⁵³, C. H. Kim¹⁷, D. Y. Kim⁷⁷, K.-H. Kim⁹⁴, S. H. Kim⁷⁶, Y.-K. Kim⁹⁴, P. Kodyš⁵, T. Konno⁴¹, A. Korobov^4,67, S. Korpar^52,36, E. Kovalenko^4,67, P. Križan^48,36, R. Kroeger⁵⁵, P. Krokovny^4,67, T. Kuhr⁴⁹, R. Kulasiri³⁹, K. Kumara⁹², Y.-J. Kwon⁹⁴, Y.-T. Lai³⁸, J. S. Lange¹², M. Laurenza^33,74, S. C. Lee⁴⁵, J. Li⁴⁵, L. K. Li⁷, Y. B. Li⁷¹, L. Li Gioi⁵³, J. Libby²⁷, K. Lieret⁴⁹, D. Liventsev^92,19, C. MacQueen⁵⁴, M. Masuda^87,73, T. Matsuda⁵⁶, D. Matvienko^4,67,47, M. Merola^32,59, F. Metzner³⁷, K. Miyabayashi⁶⁰, R. Mizuk^47,20, G. B. Mohanty⁸², R. Mussa³⁴, M. Nakao^19,15, Z. Natkaniec⁶⁴, A. Natochii¹⁸, L. Nayak²⁶, M. Nayak⁸⁴, M. Niiyama⁴⁴, N. K. Nisar³, S. Nishida^19,15, S. Ogawa⁸⁵, H. Ono^65,66, Y. Onuki⁸⁸, P. Oskin⁴⁷, P. Pakhlov^47,57, G. Pakhlova^20,47, S. Pardi³², H. Park⁴⁵, S.-H. Park¹⁹, A. Passeri³³, S. Paul^83,53, T. K. Pedlar⁵⁰, R. Pestotnik³⁶, L. E. Piilonen⁹¹, T. Podobnik^48,36, E. Prencipe²¹, M. T. Prim², I. Ripp-Baudot⁷⁸, A. Rostomyan⁸, N. Rout²⁷, G. Russo⁵⁹, D. Sahoo⁸², S. Sandilya²⁶, A. Sangal⁷, L. Santelj^48,36, T. Sanuki⁸⁶, V. Savinov⁷², G. Schnell^1,22, J. Schueler¹⁸, C. Schwanda³⁰, Y. Seino⁶⁶, K. Senyo⁹³, M. E. Sevior⁵⁴, M. Shapkin³¹, C. Sharma⁵¹, C. P. Shen¹¹, J.-G. Shiu⁶³, F. Simon⁵³, A. Sokolov³¹, E. Solovieva⁴⁷, M. Starič³⁶, Z. S. Stottler⁹¹, M. Sumihama¹³, K. Sumisawa^19,15, T. Sumiyoshi⁹⁰, W. Sutcliffe², U. Tamponi³⁴, K. Tanida³⁵, Y. Tao⁹, F. Tenchini⁸, K. Trabelsi⁴⁶, M. Uchida⁸⁹, T. Uglov^47,20, Y. Unno¹⁷, K. Uno⁶⁶, S. Uno^19,15, P. Urquijo⁵⁴, S. E. Vahsen¹⁸, R. Van Tonder², G. Varner¹⁸, K. E. Varvell⁸⁰, A. Vinokurova^4,67, E. Waheed¹⁹, C. H. Wang⁶², E. Wang⁷², M.-Z. Wang⁶³, P. Wang²⁹, X. L. Wang¹¹, M. Watanabe⁶⁶, S. Watanuki⁴⁶, J. Wiechczynski⁶⁴, E. Won⁴³, B. D. Yabsley⁸⁰, W. Yan⁷⁵, S. B. Yang⁴³, H. Ye⁸, J. Yelton⁹, J. H. Yin⁴³, Z. P. Zhang⁷⁵, V. Zhilich^4,67, and V. Zhukova⁴⁷ (The Belle Collaboration)

¹Department of Physics, University of the Basque Country UPV/EHU, 48080 Bilbao
²University of Bonn, 53115 Bonn
³Brookhaven National Laboratory, Upton, New York 11973
⁴Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090
⁵Faculty of Mathematics and Physics, Charles University, 121 16 Prague
⁶Chonnam National University, Gwangju 61186
⁷University of Cincinnati, Cincinnati, Ohio 45221
⁸Deutsches Electronen-Synchrotron, 22607 Hamburg
⁹University of Florida, Gainesville, Florida 32611
¹⁰Department of Physics, Fu Jen Catholic University, Taipei 24205
¹¹Key Laboratory of Nuclear Physics and Ion-beam Application (MOE) and Institute of Modern Physics, Fudan University, Shanghai 200443
¹²Justus-Liebig-Universität Gießen, 35392 Gießen
¹³Gifu University, Gifu 501-1193
¹⁴II. Physikalisches Institut, Georg-August-Universität Göttingen, 37073 Göttingen
¹⁵SOKENDAI (The Graduate University for Advanced Studies), Hayama 240-0193
¹⁶Gyeongsang National University, Jinju 52828
¹⁷Department of Physics and Institute of Natural Sciences, Hanyang University, Seoul 04763
¹⁸University of Hawaii, Honolulu, Hawaii 96822
¹⁹High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801
²⁰National Research University Higher School of Economics, Moscow 101000
²¹Forschungszentrum Jülich, 52425 Jülich
²²IKERBASQUE, Basque Foundation for Science, 48013 Bilbao
²³Indian Institute of Science Education and Research Mohali, SAS Nagar 140306
²⁴Indian Institute of Technology Bhubaneswar, Satya Nagar 751007
²⁵Indian Institute of Technology Guwahati, Assam 781039
²⁶Indian Institute of Technology Hyderabad, Telangana 502285
²⁷Indian Institute of Technology Madras, Chennai 600036
²⁸Indiana University, Bloomington, Indiana 47408
²⁹Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049
³⁰Institute of High Energy Physics, Vienna 1050
³¹Institute for High Energy Physics, Protvino 142281
³²INFN—Sezione di Napoli, I-80126 Napoli
³³INFN—Sezione di Roma Tre, I-00146 Rome
³⁴INFN—Sezione di Torino, I-10125 Torino
³⁵Advanced Science Research Center, Japan Atomic Energy Agency, Naka 319-1195
³⁶J. Stefan Institute, 1000 Ljubljana
³⁷Institut für Experimentelle Teilchenphysik, Karlsruher Institut für Technologie, 76131 Karlsruhe
³⁸Kavli Institute for the Physics and Mathematics of the Universe (WPI), University of Tokyo, Kashiwa 277-8583
³⁹Kennesaw State University, Kennesaw, Georgia 30144
⁴⁰Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah 21589
⁴¹Kitasato University, Sagamihara 252-0373
⁴²Korea Institute of Science and Technology Information, Daejeon 34141
⁴³Korea University, Seoul 02841
⁴⁴Kyoto Sangyo University, Kyoto 603-8555
⁴⁵Kyungpook National University, Daegu 41566
⁴⁶Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay
⁴⁷P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991
⁴⁸Faculty of Mathematics and Physics, University of Ljubljana, 1000 Ljubljana
⁴⁹Ludwig Maximilians University, 80539 Munich
⁵⁰Luther College, Decorah, Iowa 52101
⁵¹Malaviya National Institute of Technology Jaipur, Jaipur 302017
⁵²Faculty of Chemistry and Chemical Engineering, University of Maribor, 2000 Maribor
⁵³Max-Planck-Institut für Physik, 80805 München
⁵⁴School of Physics, University of Melbourne, Victoria 3010
⁵⁵University of Mississippi, University, Mississippi 38677
⁵⁶University of Miyazaki, Miyazaki 889-2192
⁵⁷Moscow Physical Engineering Institute, Moscow 115409
⁵⁸Graduate School of Science, Nagoya University, Nagoya 464-8602
⁵⁹Università di Napoli Federico II, I-80126 Napoli
⁶⁰Nara Women’s University, Nara 630-8506
⁶¹National Central University, Chung-li 32054
⁶²National United University, Miao Li 36003
⁶³Department of Physics, National Taiwan University, Taipei 10617
⁶⁴H. Niewodniczanski Institute of Nuclear Physics, Krakow 31-342
⁶⁵Nippon Dental University, Niigata 951-8580
⁶⁶Niigata University, Niigata 950-2181
⁶⁷Novosibirsk State University, Novosibirsk 630090
⁶⁸Osaka City University, Osaka 558-8585
⁶⁹Pacific Northwest National Laboratory, Richland, Washington 99352
⁷⁰Panjab University, Chandigarh 160014
⁷¹Peking University, Beijing 100871
⁷²University of Pittsburgh, Pittsburgh, Pennsylvania 15260
⁷³Research Center for Nuclear Physics, Osaka University, Osaka 567-0047
⁷⁴Dipartimento di Matematica e Fisica, Università di Roma Tre, I-00146 Rome
⁷⁵Department of Modern Physics and State Key Laboratory of Particle Detection and Electronics, University of Science and Technology of China, Hefei 230026
⁷⁶Seoul National University, Seoul 08826
⁷⁷Soongsil University, Seoul 06978
⁷⁸Université de Strasbourg, CNRS, IPHC, UMR 7178, 67037 Strasbourg
⁷⁹Sungkyunkwan University, Suwon 16419
⁸⁰School of Physics, University of Sydney, New South Wales 2006
⁸¹Department of Physics, Faculty of Science, University of Tabuk, Tabuk 71451
⁸²Tata Institute of Fundamental Research, Mumbai 400005
⁸³Department of Physics, Technische Universität München, 85748 Garching
⁸⁴School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978
⁸⁵Toho University, Funabashi 274-8510
⁸⁶Department of Physics, Tohoku University, Sendai 980-8578
⁸⁷Earthquake Research Institute, University of Tokyo, Tokyo 113-0032
⁸⁸Department of Physics, University of Tokyo, Tokyo 113-0033
⁸⁹Tokyo Institute of Technology, Tokyo 152-8550
⁹⁰Tokyo Metropolitan University, Tokyo 192-0397
⁹¹Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061
⁹²Wayne State University, Detroit, Michigan 48202
⁹³Yamagata University, Yamagata 990-8560
⁹⁴Yonsei University, Seoul 03722

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Phys. Rev. D 104, L091105 – Published 29 November, 2021

DOI: https://doi.org/10.1103/PhysRevD.104.L091105

Abstract

We present a search for the lepton-flavor-violating decays $B^{0} \to τ^{\pm} ℓ^{\mp}$ , where $ℓ = (e, μ)$ , using the full data sample of $772 \times 10^{6} B \bar{B}$ pairs recorded by the Belle detector at the KEKB asymmetric-energy $e^{+} e^{-}$ collider. We use events in which one $B$ meson is fully reconstructed in a hadronic decay mode. The $τ^{\pm}$ lepton is reconstructed indirectly using the momentum of the reconstructed $B$ and that of the $ℓ^{\mp}$ from the signal decay. We find no evidence for $B^{0} \to τ^{\pm} ℓ^{\mp}$ decays and set upper limits on their branching fractions at 90% confidence level of $B (B^{0} \to τ^{\pm} μ^{\mp}) < 1.5 \times 10^{- 5}$ and $B (B^{0} \to τ^{\pm} e^{\mp}) < 1.6 \times 10^{- 5}$ .

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Throughout this paper, charge-conjugate modes are implicitly included unless noted otherwise.
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Phys. Rev. D 104, L091105– Published 29 November, 2021

Vol. 104, Iss. 9 — 1 November 2021

Received 22 August 2021
Accepted 18 October 2021

DOI: https://doi.org/10.1103/PhysRevD.104.L091105

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

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Search for $B^{0} \to τ^{\pm} ℓ^{\mp}$ ( $ℓ = e$ , $μ$ ) with a hadronic tagging method at Belle

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Search for B0→τ±ℓ∓ (ℓ=e, μ) with a hadronic tagging method at Belle

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Search for $B^{0} \to τ^{\pm} ℓ^{\mp}$ ( $ℓ = e$ , $μ$ ) with a hadronic tagging method at Belle