Search for $B{}^0_s \rightarrow \ell^{\mp} \tau^{\pm}$ with the
Semi-leptonic Tagging Method at Belle
Belle Collaboration,L. Nayak,S. Nishida,A. Giri,I. Adachi,H. Aihara,D. M. Asner,H. Atmacan,V. Aulchenko,T. Aushev,R. Ayad,V. Babu,S. Bahinipati,Sw. Banerjee,M. Bauer,P. Behera,K. Belous,J. Bennett,M. Bessner,B. Bhuyan,D. Biswas,D. Bodrov,J. Borah,A. Bozek,M. Bračko,P. Branchini,T. E. Browder,A. Budano,M. Campajola,D. Červenkov,M. -C. Chang,B. G. Cheon,K. Chilikin,H. E. Cho,K. Cho,S. -K. Choi,Y. Choi,S. Choudhury,D. Cinabro,J. Cochran,S. Das,N. Dash,G. De Nardo,G. De Pietro,R. Dhamija,F. Di Capua,J. Dingfelder,Z. Doležal,T. V. Dong,D. Dossett,S. Dubey,D. Epifanov,T. Ferber,D. Ferlewicz,B. G. Fulsom,R. Garg,V. Gaur,P. Goldenzweig,E. Graziani,T. Gu,Y. Guan,S. Halder,T. Hara,K. Hayasaka,H. Hayashii,M. T. Hedges,D. Herrmann,W. -S. Hou,C. -L. Hsu,T. Iijima,K. Inami,G. Inguglia,N. Ipsita,A. Ishikawa,R. Itoh,M. Iwasaki,W. W. Jacobs,E. -J. Jang,S. Jia,Y. Jin,K. K. Joo,A. B. Kaliyar,T. Kawasaki,C. Kiesling,C. H. Kim,D. Y. Kim,K. -H. Kim,Y. -K. Kim,K. Kinoshita,P. Kodyš,T. Konno,A. Korobov,S. Korpar,E. Kovalenko,P. Križan,P. Krokovny,T. Kuhr,M. Kumar,R. Kumar,K. Kumara,A. Kuzmin,Y. -J. Kwon,S. C. Lee,J. Li,L. K. Li,Y. Li,J. Libby,K. Lieret,Y. -R. Lin,D. Liventsev,T. Luo,Y. Ma,M. Masuda,T. Matsuda,S. K. Maurya,F. Meier,M. Merola,F. Metzner,K. Miyabayashi,R. Mizuk,G. B. Mohanty,I. Nakamura,M. Nakao,Z. Natkaniec,A. Natochii,N. K. Nisar,S. Ogawa,H. Ono,P. Oskin,P. Pakhlov,G. Pakhlova,T. Pang,S. Pardi,J. Park,S. -H. Park,A. Passeri,S. Paul,T. K. Pedlar,R. Pestotnik,L. E. Piilonen,T. Podobnik,E. Prencipe,M. T. Prim,A. Rostomyan,N. Rout,G. Russo,S. Sandilya,A. Sangal,L. Santelj,V. Savinov,G. Schnell,C. Schwanda,A. J. Schwartz,Y. Seino,K. Senyo,M. E. Sevior,M. Shapkin,C. Sharma,J. -G. Shiu,A. Sibidanov,E. Solovieva,M. Starič,M. Sumihama,T. Sumiyoshi,M. Takizawa,K. Tanida,F. Tenchini,K. Trabelsi,M. Uchida,Y. Unno,K. Uno,S. Uno,P. Urquijo,S. E. Vahsen,G. Varner,K. E. Varvell,A. Vinokurova,D. Wang,M. -Z. Wang,S. Watanuki,E. Won,B. D. Yabsley,W. Yan,J. Yelton,Y. Yook,C. Z. Yuan,L. Yuan,Y. Yusa,Y. Zhai,Z. P. Zhang,V. Zhilich,V. Zhukova
arxiv(2023)
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摘要
We present a search for the lepton-flavor-violating decays $B{}^0_s \rightarrow \ell^{\mp}\tau^{\pm}$, where $\ell = e, \mu$, using the full data sample of $121~\mathrm{fb}^{-1}$ collected at the $\Upsilon(5S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. We use $B{}^0_s \overline{B}{}^0_s$ events in which one $B{}^0_s$ meson is reconstructed in a semileptonic decay mode and the other in the signal mode. We find no evidence for $B{}^0_s \rightarrow \ell^{\mp}\tau^{\pm}$ decays and set upper limits on their branching fractions at $90\%$ confidence level as $\mathcal{B}(B{}^0_s \rightarrow e^{\mp}\tau^{\pm}) < 14.1 \times 10^{-4}$ and $\mathcal{B}(B{}^0_s \rightarrow \mu^{\mp}\tau^{\pm}) < 7.3 \times 10^{-4}$. Our result represents the first upper limit on the $B{}^0_s \rightarrow e^{\mp}\tau^{\pm}$ decay rate.