학술논문
Test of lepton flavor universality and search for lepton flavor violation in B → Kℓℓ decays
Document Type
article
Author
The BELLE collaboration; S. Choudhury; S. Sandilya; K. Trabelsi; A. Giri; H. Aihara; S. Al Said; D. M. Asner; H. Atmacan; V. Aulchenko; T. Aushev; R. Ayad; V. Babu; S. Bahinipati; P. Behera; C. Beleño; K. Belous; J. Bennett; F. Bernlochner; M. Bessner; V. Bhardwaj; T. Bilka; J. Biswal; G. Bonvicini; A. Bozek; M. Bračko; T. E. Browder; M. Campajola; D. Červenkov; M.-C. Chang; P. Chang; V. Chekelian; A. Chen; B. G. Cheon; K. Chilikin; K. Cho; S.-K. Choi; Y. Choi; D. Cinabro; S. Cunliffe; N. Dash; G. De Nardo; R. Dhamija; F. Di Capua; J. Dingfelder; Z. Doležal; T. V. Dong; D. Dossett; S. Dubey; S. Eidelman; D. Epifanov; T. Ferber; D. Ferlewicz; B. G. Fulsom; R. Garg; V. Gaur; N. Gabyshev; A. Garmash; P. Goldenzweig; B. Golob; D. Greenwald; C. Hadjivasiliou; O. Hartbrich; H. Hayashii; M. T. Hedges; M. Hernandez Villanueva; T. Higuchi; W.-S. Hou; C.-L. Hsu; T. Iijima; K. Inami; A. Ishikawa; R. Itoh; M. Iwasaki; Y. Iwasaki; W. W. Jacobs; E.-J. Jang; H. B. Jeon; S. Jia; Y. Jin; C. W. Joo; K. K. Joo; J. Kahn; A. B. Kaliyar; K. H. Kang; G. Karyan; H. Kichimi; C. Kiesling; B. H. Kim; D. Y. Kim; K.-H. Kim; K. T. Kim; S. H. Kim; Y.-K. Kim; K. Kinoshita; P. Kodyš; S. Korpar; D. Kotchetkov; P. Križan; R. Kroeger; P. Krokovny; T. Kuhr; R. Kulasiri; R. Kumar; K. Kumara; A. Kuzmin; Y.-J. Kwon; K. Lalwani; S. C. Lee; P. Lewis; C. H. Li; L. K. Li; Y. B. Li; L. Li Gioi; J. Libby; K. Lieret; Z. Liptak; D. Liventsev; T. Luo; M. Masuda; T. Matsuda; D. Matvienko; M. Merola; K. Miyabayashi; R. Mizuk; G. B. Mohanty; S. Mohanty; T. J. Moon; T. Mori; I. Nakamura; K. R. Nakamura; M. Nakao; Z. Natkaniec; A. Natochii; L. Nayak; M. Nayak; M. Niiyama; N. K. Nisar; S. Nishida; K. Ogawa; H. Ono; Y. Onuki; P. Oskin; P. Pakhlov; G. Pakhlova; S. Pardi; H. Park; S.-H. Park; S. Patra; S. Paul; T. K. Pedlar; R. Pestotnik; L. E. Piilonen; T. Podobnik; V. Popov; E. Prencipe; M. T. Prim; A. Rabusov; A. Rostomyan; N. Rout; M. Rozanska; G. Russo; D. Sahoo; Y. Sakai; L. Santelj; T. Sanuki; V. Savinov; G. Schnell; J. Schueler; C. Schwanda; A. J. Schwartz; Y. Seino; K. Senyo; M. E. Sevior; M. Shapkin; V. Shebalin; J.-G. Shiu; B. Shwartz; F. Simon; A. Sokolov; E. Solovieva; S. Stanič; M. Starič; Z. S. Stottler; T. Sumiyoshi; W. Sutcliffe; M. Takizawa; U. Tamponi; K. Tanida; F. Tenchini; M. Uchida; S. Uehara; T. Uglov; Y. Unno; S. Uno; P. Urquijo; Y. Ushiroda; R. Van Tonder; G. Varner; K. E. Varvell; A. Vinokurova; V. Vorobyev; E. Waheed; C. H. Wang; E. Wang; M.-Z. Wang; P. Wang; M. Watanabe; S. Watanuki; S. Wehle; J. Wiechczynski; E. Won; X. Xu; B. D. Yabsley; W. Yan; S. B. Yang; H. Ye; J. Yelton; J. H. Yin; C. Z. Yuan; Y. Yusa; Z. P. Zhang; V. Zhilich; V. Zhukova
Source
Journal of High Energy Physics, Vol 2021, Iss 3, Pp 1-24 (2021)
Subject
Language
English
ISSN
1029-8479
Abstract
Abstract We present measurements of the branching fractions for the decays B → Kμ + μ − and B → Ke + e − , and their ratio (R K ), using a data sample of 711 fb −1 that contains 772 × 106 B B ¯ $$ B\overline{B} $$ events. The data were collected at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e + e − collider. The ratio R K is measured in five bins of dilepton invariant-mass-squared (q 2): q 2 ∈ (0.1, 4.0), (4.00, 8.12), (1.0, 6.0), (10.2, 12.8) and (> 14.18) GeV2 /c 4, along with the whole q 2 region. The R K value for q 2 ∈ (1.0, 6.0) GeV2 /c 4 is 1.03 − 0.24 + 0.28 $$ {1.03}_{-0.24}^{+0.28} $$ ± 0.01. The first and second uncertainties listed are statistical and systematic, respectively. All results for R K are consistent with Standard Model predictions. We also measure CP-averaged isospin asymmetries in the same q 2 bins. The results are consistent with a null asymmetry, with the largest difference of 2.6 standard deviations occurring for the q 2 ∈ (1.0, 6.0) GeV2 /c 4 bin in the mode with muon final states. The measured differential branching fractions, d ℬ $$ d\mathrm{\mathcal{B}} $$ /dq 2, are consistent with theoretical predictions for charged B decays, while the corresponding values are below the expectations for neutral B decays. We have also searched for lepton-flavor-violating B → Kμ ± e ∓ decays and set 90% confidence-level upper limits on the branching fraction in the range of 10 −8 for B + → K + μ ± e ∓, and B 0 → K 0 μ ± e ∓ modes.