Test of lepton flavor universality and search for lepton flavor violation in B → Kℓℓ decays
oleh: 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
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| Diterbitkan: | SpringerOpen 2021-03-01 |
Deskripsi
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.