This paper was converted on www.awesomepapers.org from LaTeX by an anonymous user.
Want to know more? Visit the Converter page.

The Belle Collaboration

Study of 𝑩¯𝟎𝑫+𝒉(𝒉=𝑲/𝝅)\overline{B}{}^{0}\rightarrow D^{+}h^{-}(h=K/\pi) decays at Belle

E. Waheed High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801    P. Urquijo School of Physics, University of Melbourne, Victoria 3010    I. Adachi High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801 SOKENDAI (The Graduate University for Advanced Studies), Hayama 240-0193    H. Aihara Department of Physics, University of Tokyo, Tokyo 113-0033    S. Al Said Department of Physics, Faculty of Science, University of Tabuk, Tabuk 71451 Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah 21589    D. M. Asner Brookhaven National Laboratory, Upton, New York 11973    H. Atmacan University of Cincinnati, Cincinnati, Ohio 45221    V. Aulchenko Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090 Novosibirsk State University, Novosibirsk 630090    T. Aushev National Research University Higher School of Economics, Moscow 101000    S. Bahinipati Indian Institute of Technology Bhubaneswar, Satya Nagar 751007    P. Behera Indian Institute of Technology Madras, Chennai 600036    K. Belous Institute for High Energy Physics, Protvino 142281    J. Bennett University of Mississippi, University, Mississippi 38677    M. Bessner University of Hawaii, Honolulu, Hawaii 96822    V. Bhardwaj Indian Institute of Science Education and Research Mohali, SAS Nagar, 140306    B. Bhuyan Indian Institute of Technology Guwahati, Assam 781039    T. Bilka Faculty of Mathematics and Physics, Charles University, 121 16 Prague    J. Biswal J. Stefan Institute, 1000 Ljubljana    A. Bobrov Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090 Novosibirsk State University, Novosibirsk 630090    D. Bodrov National Research University Higher School of Economics, Moscow 101000 P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991    J. Borah Indian Institute of Technology Guwahati, Assam 781039    A. Bozek H. Niewodniczanski Institute of Nuclear Physics, Krakow 31-342    M. Bračko Faculty of Chemistry and Chemical Engineering, University of Maribor, 2000 Maribor J. Stefan Institute, 1000 Ljubljana    P. Branchini INFN - Sezione di Roma Tre, I-00146 Roma    T. E. Browder University of Hawaii, Honolulu, Hawaii 96822    A. Budano INFN - Sezione di Roma Tre, I-00146 Roma    M. Campajola INFN - Sezione di Napoli, I-80126 Napoli Università di Napoli Federico II, I-80126 Napoli    D. Červenkov Faculty of Mathematics and Physics, Charles University, 121 16 Prague    M.-C. Chang Department of Physics, Fu Jen Catholic University, Taipei 24205    P. Chang Department of Physics, National Taiwan University, Taipei 10617    A. Chen National Central University, Chung-li 32054    B. G. Cheon Department of Physics and Institute of Natural Sciences, Hanyang University, Seoul 04763    K. Chilikin P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991    H. E. Cho Department of Physics and Institute of Natural Sciences, Hanyang University, Seoul 04763    K. Cho Korea Institute of Science and Technology Information, Daejeon 34141    S.-J. Cho Yonsei University, Seoul 03722    S.-K. Choi Gyeongsang National University, Jinju 52828    Y. Choi Sungkyunkwan University, Suwon 16419    S. Choudhury Indian Institute of Technology Hyderabad, Telangana 502285    D. Cinabro Wayne State University, Detroit, Michigan 48202    S. Cunliffe Deutsches Elektronen–Synchrotron, 22607 Hamburg    S. Das Malaviya National Institute of Technology Jaipur, Jaipur 302017    G. De Nardo INFN - Sezione di Napoli, I-80126 Napoli Università di Napoli Federico II, I-80126 Napoli    G. De Pietro INFN - Sezione di Roma Tre, I-00146 Roma    R. Dhamija Indian Institute of Technology Hyderabad, Telangana 502285    F. Di Capua INFN - Sezione di Napoli, I-80126 Napoli Università di Napoli Federico II, I-80126 Napoli    Z. Doležal Faculty of Mathematics and Physics, Charles University, 121 16 Prague    T. V. Dong Key Laboratory of Nuclear Physics and Ion-beam Application (MOE) and Institute of Modern Physics, Fudan University, Shanghai 200443    D. Epifanov Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090 Novosibirsk State University, Novosibirsk 630090    T. Ferber Deutsches Elektronen–Synchrotron, 22607 Hamburg    D. Ferlewicz School of Physics, University of Melbourne, Victoria 3010    B. G. Fulsom Pacific Northwest National Laboratory, Richland, Washington 99352    R. Garg Panjab University, Chandigarh 160014    V. Gaur Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061    N. Gabyshev Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090 Novosibirsk State University, Novosibirsk 630090    A. Giri Indian Institute of Technology Hyderabad, Telangana 502285    P. Goldenzweig Institut für Experimentelle Teilchenphysik, Karlsruher Institut für Technologie, 76131 Karlsruhe    B. Golob Faculty of Mathematics and Physics, University of Ljubljana, 1000 Ljubljana J. Stefan Institute, 1000 Ljubljana    E. Graziani INFN - Sezione di Roma Tre, I-00146 Roma    T. Gu University of Pittsburgh, Pittsburgh, Pennsylvania 15260    Y. Guan University of Cincinnati, Cincinnati, Ohio 45221    K. Gudkova Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090 Novosibirsk State University, Novosibirsk 630090    C. Hadjivasiliou Pacific Northwest National Laboratory, Richland, Washington 99352    S. Halder Tata Institute of Fundamental Research, Mumbai 400005    O. Hartbrich University of Hawaii, Honolulu, Hawaii 96822    K. Hayasaka Niigata University, Niigata 950-2181    H. Hayashii Nara Women’s University, Nara 630-8506    W.-S. Hou Department of Physics, National Taiwan University, Taipei 10617    C.-L. Hsu School of Physics, University of Sydney, New South Wales 2006    T. Iijima Kobayashi-Maskawa Institute, Nagoya University, Nagoya 464-8602 Graduate School of Science, Nagoya University, Nagoya 464-8602    K. Inami Graduate School of Science, Nagoya University, Nagoya 464-8602    A. Ishikawa High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801 SOKENDAI (The Graduate University for Advanced Studies), Hayama 240-0193    R. Itoh High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801 SOKENDAI (The Graduate University for Advanced Studies), Hayama 240-0193    M. Iwasaki Osaka City University, Osaka 558-8585    Y. Iwasaki High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801    W. W. Jacobs Indiana University, Bloomington, Indiana 47408    S. Jia Key Laboratory of Nuclear Physics and Ion-beam Application (MOE) and Institute of Modern Physics, Fudan University, Shanghai 200443    Y. Jin Department of Physics, University of Tokyo, Tokyo 113-0033    K. K. Joo Chonnam National University, Gwangju 61186    A. B. Kaliyar Tata Institute of Fundamental Research, Mumbai 400005    K. H. Kang Kyungpook National University, Daegu 41566    H. Kichimi High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801    C. H. Kim Department of Physics and Institute of Natural Sciences, Hanyang University, Seoul 04763    D. Y. Kim Soongsil University, Seoul 06978    K.-H. Kim Yonsei University, Seoul 03722    K. T. Kim Korea University, Seoul 02841    Y.-K. Kim Yonsei University, Seoul 03722    K. Kinoshita University of Cincinnati, Cincinnati, Ohio 45221    P. Kodyš Faculty of Mathematics and Physics, Charles University, 121 16 Prague    T. Konno Kitasato University, Sagamihara 252-0373    A. Korobov Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090 Novosibirsk State University, Novosibirsk 630090    S. Korpar Faculty of Chemistry and Chemical Engineering, University of Maribor, 2000 Maribor J. Stefan Institute, 1000 Ljubljana    E. Kovalenko Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090 Novosibirsk State University, Novosibirsk 630090    P. Križan Faculty of Mathematics and Physics, University of Ljubljana, 1000 Ljubljana J. Stefan Institute, 1000 Ljubljana    R. Kroeger University of Mississippi, University, Mississippi 38677    P. Krokovny Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090 Novosibirsk State University, Novosibirsk 630090    M. Kumar Malaviya National Institute of Technology Jaipur, Jaipur 302017    R. Kumar Punjab Agricultural University, Ludhiana 141004    K. Kumara Wayne State University, Detroit, Michigan 48202    Y.-J. Kwon Yonsei University, Seoul 03722    Y.-T. Lai Kavli Institute for the Physics and Mathematics of the Universe (WPI), University of Tokyo, Kashiwa 277-8583    J. S. Lange Justus-Liebig-Universität Gießen, 35392 Gießen    M. Laurenza INFN - Sezione di Roma Tre, I-00146 Roma Dipartimento di Matematica e Fisica, Università di Roma Tre, I-00146 Roma    S. C. Lee Kyungpook National University, Daegu 41566    J. Li Kyungpook National University, Daegu 41566    L. K. Li University of Cincinnati, Cincinnati, Ohio 45221    Y. B. Li Peking University, Beijing 100871    L. Li Gioi Max-Planck-Institut für Physik, 80805 München    J. Libby Indian Institute of Technology Madras, Chennai 600036    K. Lieret Ludwig Maximilians University, 80539 Munich    D. Liventsev Wayne State University, Detroit, Michigan 48202 High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801    C. MacQueen School of Physics, University of Melbourne, Victoria 3010    M. Masuda Earthquake Research Institute, University of Tokyo, Tokyo 113-0032 Research Center for Nuclear Physics, Osaka University, Osaka 567-0047    T. Matsuda University of Miyazaki, Miyazaki 889-2192    M. Merola INFN - Sezione di Napoli, I-80126 Napoli Università di Napoli Federico II, I-80126 Napoli    F. Metzner Institut für Experimentelle Teilchenphysik, Karlsruher Institut für Technologie, 76131 Karlsruhe    K. Miyabayashi Nara Women’s University, Nara 630-8506    R. Mizuk P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991 National Research University Higher School of Economics, Moscow 101000    G. B. Mohanty Tata Institute of Fundamental Research, Mumbai 400005    R. Mussa INFN - Sezione di Torino, I-10125 Torino    M. Nakao High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801 SOKENDAI (The Graduate University for Advanced Studies), Hayama 240-0193    A. Natochii University of Hawaii, Honolulu, Hawaii 96822    L. Nayak Indian Institute of Technology Hyderabad, Telangana 502285    M. Nayak School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978    M. Niiyama Kyoto Sangyo University, Kyoto 603-8555    N. K. Nisar Brookhaven National Laboratory, Upton, New York 11973    S. Nishida High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801 SOKENDAI (The Graduate University for Advanced Studies), Hayama 240-0193    S. Ogawa Toho University, Funabashi 274-8510    H. Ono Nippon Dental University, Niigata 951-8580 Niigata University, Niigata 950-2181    P. Oskin P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991    P. Pakhlov P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991 Moscow Physical Engineering Institute, Moscow 115409    G. Pakhlova National Research University Higher School of Economics, Moscow 101000 P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991    T. Pang University of Pittsburgh, Pittsburgh, Pennsylvania 15260    H. Park Kyungpook National University, Daegu 41566    S.-H. Park High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801    A. Passeri INFN - Sezione di Roma Tre, I-00146 Roma    S. Patra Indian Institute of Science Education and Research Mohali, SAS Nagar, 140306    S. Paul Department of Physics, Technische Universität München, 85748 Garching Max-Planck-Institut für Physik, 80805 München    T. K. Pedlar Luther College, Decorah, Iowa 52101    R. Pestotnik J. Stefan Institute, 1000 Ljubljana    L. E. Piilonen Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061    T. Podobnik Faculty of Mathematics and Physics, University of Ljubljana, 1000 Ljubljana J. Stefan Institute, 1000 Ljubljana    V. Popov National Research University Higher School of Economics, Moscow 101000    E. Prencipe Forschungszentrum Jülich, 52425 Jülich    M. T. Prim University of Bonn, 53115 Bonn    M. Röhrken Deutsches Elektronen–Synchrotron, 22607 Hamburg    A. Rostomyan Deutsches Elektronen–Synchrotron, 22607 Hamburg    N. Rout Indian Institute of Technology Madras, Chennai 600036    G. Russo Università di Napoli Federico II, I-80126 Napoli    D. Sahoo Tata Institute of Fundamental Research, Mumbai 400005    S. Sandilya Indian Institute of Technology Hyderabad, Telangana 502285    L. Santelj Faculty of Mathematics and Physics, University of Ljubljana, 1000 Ljubljana J. Stefan Institute, 1000 Ljubljana    T. Sanuki Department of Physics, Tohoku University, Sendai 980-8578    V. Savinov University of Pittsburgh, Pittsburgh, Pennsylvania 15260    G. Schnell Department of Physics, University of the Basque Country UPV/EHU, 48080 Bilbao IKERBASQUE, Basque Foundation for Science, 48013 Bilbao    C. Schwanda Institute of High Energy Physics, Vienna 1050    A. J. Schwartz University of Cincinnati, Cincinnati, Ohio 45221    Y. Seino Niigata University, Niigata 950-2181    K. Senyo Yamagata University, Yamagata 990-8560    M. E. Sevior School of Physics, University of Melbourne, Victoria 3010    M. Shapkin Institute for High Energy Physics, Protvino 142281    C. Sharma Malaviya National Institute of Technology Jaipur, Jaipur 302017    C. P. Shen Key Laboratory of Nuclear Physics and Ion-beam Application (MOE) and Institute of Modern Physics, Fudan University, Shanghai 200443    J.-G. Shiu Department of Physics, National Taiwan University, Taipei 10617    F. Simon Max-Planck-Institut für Physik, 80805 München    J. B. Singh Panjab University, Chandigarh 160014    A. Sokolov Institute for High Energy Physics, Protvino 142281    E. Solovieva P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991    M. Starič J. Stefan Institute, 1000 Ljubljana    Z. S. Stottler Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061    J. F. Strube Pacific Northwest National Laboratory, Richland, Washington 99352    M. Sumihama Gifu University, Gifu 501-1193    T. Sumiyoshi Tokyo Metropolitan University, Tokyo 192-0397    W. Sutcliffe University of Bonn, 53115 Bonn    M. Takizawa Showa Pharmaceutical University, Tokyo 194-8543 J-PARC Branch, KEK Theory Center, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801 Meson Science Laboratory, Cluster for Pioneering Research, RIKEN, Saitama 351-0198    U. Tamponi INFN - Sezione di Torino, I-10125 Torino    K. Tanida Advanced Science Research Center, Japan Atomic Energy Agency, Naka 319-1195    F. Tenchini Deutsches Elektronen–Synchrotron, 22607 Hamburg    K. Trabelsi Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay    M. Uchida Tokyo Institute of Technology, Tokyo 152-8550    T. Uglov P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991 National Research University Higher School of Economics, Moscow 101000    Y. Unno Department of Physics and Institute of Natural Sciences, Hanyang University, Seoul 04763    K. Uno Niigata University, Niigata 950-2181    S. Uno High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801 SOKENDAI (The Graduate University for Advanced Studies), Hayama 240-0193    Y. Usov Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090 Novosibirsk State University, Novosibirsk 630090    S. E. Vahsen University of Hawaii, Honolulu, Hawaii 96822    R. Van Tonder University of Bonn, 53115 Bonn    G. Varner University of Hawaii, Honolulu, Hawaii 96822    K. E. Varvell School of Physics, University of Sydney, New South Wales 2006    A. Vinokurova Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090 Novosibirsk State University, Novosibirsk 630090    C. H. Wang National United University, Miao Li 36003    E. Wang University of Pittsburgh, Pittsburgh, Pennsylvania 15260    M.-Z. Wang Department of Physics, National Taiwan University, Taipei 10617    P. Wang Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049    X. L. Wang Key Laboratory of Nuclear Physics and Ion-beam Application (MOE) and Institute of Modern Physics, Fudan University, Shanghai 200443    J. Wiechczynski H. Niewodniczanski Institute of Nuclear Physics, Krakow 31-342    E. Won Korea University, Seoul 02841    B. D. Yabsley School of Physics, University of Sydney, New South Wales 2006    W. Yan Department of Modern Physics and State Key Laboratory of Particle Detection and Electronics, University of Science and Technology of China, Hefei 230026    S. B. Yang Korea University, Seoul 02841    H. Ye Deutsches Elektronen–Synchrotron, 22607 Hamburg    J. Yelton University of Florida, Gainesville, Florida 32611    J. H. Yin Korea University, Seoul 02841    Y. Yusa Niigata University, Niigata 950-2181    Z. P. Zhang Department of Modern Physics and State Key Laboratory of Particle Detection and Electronics, University of Science and Technology of China, Hefei 230026    V. Zhilich Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090 Novosibirsk State University, Novosibirsk 630090    V. Zhukova P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991
Abstract

We present a measurement of the branching fractions of the Cabibbo favored B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} and the Cabibbo suppressed B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} decays. We find (B¯0D+π)=(2.48±0.01±0.09±0.04)×103\mathcal{B}(\overline{B}{}^{0}\rightarrow D^{+}\pi^{-})=(2.48\pm 0.01\pm 0.09\pm 0.04)\times 10^{-3} and (B¯0D+K)=(2.03±0.05±0.07±0.03)×104\mathcal{B}(\overline{B}{}^{0}\rightarrow D^{+}K^{-})=(2.03\pm 0.05\pm 0.07\pm 0.03)\times 10^{-4} decays, where the first uncertainty is statistical, the second is systematic, and the third uncertainty is due to the D+Kπ+π+D^{+}\rightarrow K^{-}\pi^{+}\pi^{+} branching fraction. The ratio of branching fractions of B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} and B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} is measured to be RD=[8.19±0.20(stat)±0.23(syst)]×102R^{D}=[8.19\pm 0.20(\rm stat)\pm 0.23(\rm syst)]\times 10^{-2}. These measurements are performed using the full Belle dataset, which corresponds to 772×106BB¯772\times 10^{6}B\overline{B} pairs and use the Belle II software framework for data analysis.

preprint: Belle Preprint 2021-25 KEK Preprint 2021-30

I Introduction

Two-body decays of BB mesons serve as an important test bed for phenomenological studies of the quark flavor sector of the Standard Model of particle physics. The Cabibbo-favored mode B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} is an especially clean and abundant hadronic decay that provides a good opportunity to test models of hadronic BB meson decays. Due to the large mass of the bb quark, the influence of the strong interaction in these decays can be calculated more reliably than those in light-meson decays. It has been suggested that improved measurements of color-favored hadronic two-body decays of BB mesons will lead to a better understanding of poorly known quantum chromodynamics (QCD) effects cite-qcdeffetcs . The decays of BB mesons to two-body hadronic final states can be analyzed by decomposing their amplitudes in terms of different decay topologies and then applying SU(3) flavor symmetry of QCD to derive relations between them. The Cabibbo-suppressed mode B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} only receives contributions from color-allowed tree amplitudes while B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} receives contributions from both color-allowed tree and exchange amplitudes cite-arXiv:1012.2784 . These two decay modes can be related by a ratio cite-belleold ,

RD\displaystyle R^{D} \displaystyle\equiv (B¯0D+K)(B¯0D+π)tan2θC(fKfπ)2,\displaystyle\frac{\mathcal{B}(\overline{B}{}^{0}\rightarrow D^{+}K^{-})}{\mathcal{B}(\overline{B}{}^{0}\rightarrow D^{+}\pi^{-})}\simeq\tan^{2}\theta_{\rm C}\left(\frac{f_{K}}{f_{\pi}}\right)^{2}, (1)

where θC\theta_{\rm C} is the Cabibbo angle, and fKf_{K} and fπf_{\pi} are meson decay constants. The theoretical description for these hadronic decays has considerably improved over the years cite-theory1 ; cite-theory2 and has been followed by several recent developments cite-arXix1606.02888 ; cite-arXiv:2007.10338 . This description relies on factorization and SU(3)-symmetry assumptions, so measurements of these modes can be used to test these hypotheses in heavy-quark hadronic decays. The above two modes are also important because they constitute high-statistics control samples for the hadronic BB-decay measurements related to time-dependent CPCP violation and the extraction of the Cabibbo-Kobayashi-Maskawa unitarity-triangle angle ϕ3\phi_{3} cite-theory3 . Experimentally, calculating the ratio of the branching fractions of B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} and B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} modes has the advantage that many systematic uncertainties cancel, enabling tests of theoretical predictions, particularly those of factorization and SU(3) symmetry breaking in QCD.

The theoretical predictions made in Refs. cite-arXix1606.02888 ; cite-arXiv:2007.10338 are based on the framework of QCD factorization, at next-to-next-to-leading order. However, these predictions significantly differ from the experimental values. Several attempts cite-arXiv:2103.04138 ; cite-arXiv:2109.04950 ; cite-arXiv:2008.01086 have been made to explain the discrepancy in both B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} and B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} decays within the context of new physics. Final-state rescattering effects on B¯0D+h(h=K/π)\overline{B}{}^{0}\rightarrow D^{+}h^{-}(h={K/\pi}) have also been proposed to explain the discrepancy cite-arXiv:2109.10811 . The results in Ref. cite-arXiv:2109.10811 rule out rescattering effects as a cause for the discrepancies and hence hint at a possible beyond-the-SM explanation.

Earlier, Belle reported a study of the Cabibbo-suppressed B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} decay using a small data datasetset cite-belleold by measuring the ratio of branching fraction of Cabibbo-suppressed B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} to that of the Cabibbo-favored B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} decay. The branching fraction for B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} decay was previously measured by BABAR cite-BaBar1 ; cite-BaBar2 , CLEO cite-cleo1 ; cite-cleo2 and ARGUS cite-argus . LHCb measured the branching fraction of B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} as well as the ratio of hadronization fractions fs/fdf_{s}/f_{d} cite-DKlhcb . A clear understanding of B¯0D+h(h=K/π)\overline{B}{}^{0}\rightarrow D^{+}h^{-}(h={K/\pi}) decays constitutes an important ingredient for the measurement fs/fdf_{s}/f_{d}, which in turn will aid the measurement of rare decay Bs0μ+μB_{s}^{0}\rightarrow\mu^{+}\mu^{-}. Currently, the world averages cite-PDG for the branching fractions of B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} and B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} decays are (B¯0D+K)=(1.86±0.20)×104\mathcal{B}(\overline{B}{}^{0}\rightarrow D^{+}K^{-})=(1.86\pm 0.20)\times 10^{-4} and (B¯0D+π)=(2.52±0.13)×103\mathcal{B}(\overline{B}{}^{0}\rightarrow D^{+}\pi^{-})=(2.52\pm 0.13)\times 10^{-3}, respectively, where the uncertainty is the sum in quadrature of the statistical and systematic errors. LHCb cite-ratiolhcb measured the ratio of the branching fractions for B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} and B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} to be 0.0822±0.0011(stat)±0.0025(syst)0.0822\pm 0.0011(\rm stat)\pm 0.0025(\rm syst), which dominates the current world-average value.

In this paper, we present measurements of the branching fractions of B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} and B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} decays using the full Υ(4S)\Upsilon(4S) dataset collected with the Belle detector.

The paper is organized as follows. Sec. II describes the Belle detector, as well as the data and simulation samples used in this analysis. The event selection requirements are outlined in Sec. III. Sec. IV describes how the values of RDR^{D} and the B¯0D+h(h=K/π)\overline{B}{}^{0}\rightarrow D^{+}h^{-}(h=K/\pi) branching fraction are determined from the data. The results and the evaluation of systematic uncertainties are described in Sec. V, and the conclusion is given in Sec. VI.

II THE BELLE DETECTOR AND DATA SAMPLE

We use the full Υ(4S)\Upsilon(4S) data sample containing 772×106BB¯772\times 10^{6}~{}B\overline{B} events recorded with the Belle detector cite-Belle at the KEKB asymmetric-beam-energy e+ee^{+}e^{-} collider  cite-KEKB . Belle is a large-solid-angle magnetic spectrometer that consists of a silicon vertex detector, a 50-layer central drift chamber (CDC), an array of aerogel threshold Cherenkov counters (ACC), a barrel-like arrangement of time-of-flight scintillation counters (TOF), and an electromagnetic calorimeter comprised of CsI(Tl) crystals. All these detector components are located inside a superconducting solenoid coil that provides a 1.5 T magnetic field cite-Belle .

A Monte Carlo (MC) simulated event sample is used to optimize the event selection, study background and compare the distributions observed in collision data with expectations. A signal-only simulated event sample is utilized to model the features of the signal for fits and determine selection efficiencies. One million signal events are generated for both decay channels. The so-called generic MC sample consists of simulated events that include e+ee^{+}e^{-}\to BB¯B\overline{B}{}, uu¯u\overline{u}, dd¯d\overline{d}, ss¯s\overline{s}, and cc¯c\overline{c} processes in realistic proportions, and corresponds in size to more than five times the Υ(4S)\Upsilon(4S) data. The generic MC sample is used to study background and make comparisons with the data. The BB- and DD-meson decays are simulated with the EvtGen generator cite-EvtGen where the D_DALITZ model is used for the D+Kπ+π+D^{+}\rightarrow K^{-}\pi^{+}\pi^{+} final state. The effect of final-state radiation is simulated by the PHOTOS package cite-PHOTOS . The interactions of particles with the detector are simulated using GEANT3 cite-GEANT .

III EVENT SELECTION AND RECONSTRUCTION

We use the Belle II Analysis Software Framework (basf2) cite-basf2 for the decay-chain reconstruction and convert the Belle data to basf2 format using the B2BII software package cite-b2bii . The decays B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} and B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} have nearly the same kinematic properties. The former is used to establish selection criteria on kinematic variables and determine the experimental resolution due to its larger data size compared to the latter. Charged particle tracks originating from e+ee^{+}e^{-} collisions are selected by requiring dr<0.2cmdr<0.2~{}\rm cm and |dz|<1.5cm|dz|<1.5~{}\rm cm, where drdr and |dz||dz| represent the distance of closest approach to the interaction point (IP) in the plane transverse to and along the zz axis, respectively. The zz axis is the direction opposite the e+e^{+} beam.

Information from the CDC, ACC, and TOF is used to determine a K/πK/\pi likelihood ratio (K/π)=KK+π\mathcal{L}(K/\pi)=\frac{\mathcal{L}_{K}}{\mathcal{L}_{K}+\mathcal{L}_{\pi}} for charged particle identification (PID), where K\mathcal{L}_{K} and π\mathcal{L}_{\pi} are the likelihoods that a particular track is either a kaon or a pion, respectively. The likelihood value ranges from 0 to 1 where 0 (1) means the track is likely to be a π\pi (KK). To ensure high efficiency and purity, we require (K/π)>0.6\mathcal{L}(K/\pi)>0.6 for kaon candidates and (K/π)<0.6\mathcal{L}(K/\pi)<0.6 for pion candidates. The charged D+D^{+} candidate is formed using Kπ+π+K^{-}\pi^{+}\pi^{+} combinations, which is then combined with a prompt hadron (h=K/π)(h=K/\pi) to form a B¯0\overline{B}{}^{0} candidate. (The inclusion of charge conjugate states is implied throughout this paper.) D+D^{+} meson candidates are required to have a mass within ±2.5σ\pm 2.5\sigma of the known D+D^{+} mass value cite-PDG , where the Gaussian resolution σ\sigma is approximately 5MeV5~{}\rm MeV. The effective σ\sigma value is obtained by fitting the invariant mass distribution of D+Kπ+π+D^{+}\rightarrow K^{-}\pi^{+}\pi^{+} decays with a double Gaussian function for signal and a first-order polynomial for background as shown in Fig. 1.

Refer to caption
Figure 1: Fit to the invariant mass distribution for D+Kπ+π+D^{+}\rightarrow K^{-}\pi^{+}\pi^{+} in data. The black vertical dotted lines show the DD mass window. The dashed curve shows the signal component and dotted black line shows the background component. The distribution of pulls between the fit and the data points is also shown.

The kinematic variables used to discriminate BB decays from background are the beam-energy-constrained mass

Mbc\displaystyle M_{\rm bc} \displaystyle\equiv Ebeam2pB2,\displaystyle\sqrt{E^{2}_{\rm beam}-p^{2}_{B}}, (2)

and the energy difference

ΔE\displaystyle\Delta E \displaystyle\equiv EBEbeam.\displaystyle E_{B}-E_{\rm beam}. (3)

Here EBE_{B} and pBp_{B} are the BB candidate’s energy and momentum, respectively, and EbeamE_{\rm beam} is the beam energy; these quantities are calculated in the e+ee^{+}e^{-} center-of-mass frame. Natural units \hbar = c = 1 are used throughout the paper. For correctly reconstructed signal events, MbcM_{\rm bc} peaks at the known mass of the B¯0\overline{B}{}^{0} meson and ΔE\Delta E peaks at zero. We retain the B¯0\overline{B}{}^{0} candidates satisfying Mbc>5.27GeVM_{\rm bc}>~{}5.27~{}\rm GeV and |ΔE|<0.13GeV|\Delta E|<0.13~{}\text{GeV}.

The background from e+eqq¯e^{+}e^{-}\rightarrow q\overline{q} (q=u,d,s,c)(q=u,d,s,c) continuum processes are suppressed by requiring the ratio of the second-to-zeroth order Fox-Wolfram moments cite-r2 to be less than 0.3. This selection removes \sim70%70\% of the continuum while rejecting \sim30%30\% of the signal in both B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} and B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} decays. After applying the aforementioned selection criteria, only 0.7%0.7\% of events are found to have more than one candidate. In such events, we choose the best candidate as the one having the smallest value of |MbcmB||M_{\rm bc}-m_{B}| where mBm_{B} is the known B¯0\overline{B}{}^{0} mass. The kaon identification efficiency ϵK\epsilon_{K} is determined from a kinematically selected sample of high momentum D+D^{*+} mesons, which is used to calibrate the PID performance. With the application of the requirements (K/π)<0.6\mathcal{L}(K/\pi)<0.6 for pions and (K/π)>0.6\mathcal{L}(K/\pi)>0.6 for kaons, the kaon efficiency (ϵK\epsilon_{K}) value is found to be (84.48±0.35)%(84.48\pm 0.35)\% and the rate of pions misidentified as kaons is (7.62±0.44)%(7.62\pm 0.44)\%.

IV Simultaneous Fit

As the B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} branching fraction is an order of magnitude larger than that of B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-}, the former can serve as an excellent calibration sample for the signal determination procedure. Furthermore, there is a significant contamination from B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} decays in the B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} sample in which the fast charged pion is misidentified as a kaon. A simultaneous fit to samples enriched in prompt tracks that are identified as either pions [(K/π)<0.6][\mathcal{L}(K/\pi)<0.6] or kaons [(K/π)>0.6\mathcal{L}(K/\pi)>0.6], allows us to directly determine this cross feed contribution from data. An unbinned maximum-likelihood fit is performed to extract the signal yield by fitting the ΔE\Delta E distribution simultaneously in pion and kaon enriched samples. The yields of the B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} and B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} signals, as well as their cross feed contributions, in the pion and kaon enriched samples can be expressed by the following relations:

Npion enhancedD+π\displaystyle N^{D^{+}\pi^{-}}_{\text{pion enhanced}} =\displaystyle= (1κ)NtotalD+π,\displaystyle(1-\kappa)\,N^{D^{+}\pi^{-}}_{\rm total}, (4)
Nkaon enhancedD+π\displaystyle N^{D^{+}\pi^{-}}_{\text{kaon enhanced}} =\displaystyle= κNtotalD+π,\displaystyle\kappa\,N^{D^{+}\pi^{-}}_{\rm total}, (5)
Nkaon enhancedD+K\displaystyle N^{D^{+}K^{-}}_{\text{kaon enhanced}} =\displaystyle= ϵKRDNtotalD+π,\displaystyle\epsilon_{K}\,R^{D}\,N^{D^{+}\pi^{-}}_{\rm total}, (6)
Npion enhancedD+K\displaystyle N^{D^{+}K^{-}}_{\text{pion enhanced}} =\displaystyle= (1ϵK)RDNtotalD+π.\displaystyle(1-\epsilon_{K})\,R^{D}\,N^{D^{+}\pi^{-}}_{\rm total}. (7)

Here the values of Npion enhancedD+h(h=K/π)N^{D^{+}h^{-}}_{\text{pion enhanced}}(h=K/\pi) are the kaon and the pion yields in pion enriched sample with [(K/π)<0.6\mathcal{L}(K/\pi)<0.6], and the Nkaon enhancedD+h(h=K/π)N^{D^{+}h^{-}}_{\text{kaon enhanced}}(h=K/\pi) are the kaon and pion yields in the kaon enriched sample with [(K/π)>0.6\mathcal{L}(K/\pi)>0.6]. The pion misidentification rate κ\kappa is a free parameter, as well as RDR^{D} and NtotalD+πN^{D^{+}\pi^{-}}_{\rm total}, where the latter is the total signal yield for the B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} decay. Due to a small contribution from B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} cross feed in the pion-enriched sample, the kaon identification efficiency ϵK\epsilon_{K} is fixed to the value given in Sec. III. The yields are obtained from fitting the ΔE\Delta E distribution. The background components are divided into the following categories in the fit:

  1. 1.

    continuum qq¯q\overline{q} background and combinatorial BB¯B\overline{B} background, in which the final state particles could be from either the BB or B¯\overline{B} meson in an event; and

  2. 2.

    cross feed background from B¯0D+h\overline{B}{}^{0}\rightarrow D^{+}h^{-}, where h=π,Kh=\pi,K, in which the charged kaon is misidentified as a pion or vice versa.

The B¯0D+h(h=K/π)\overline{B}{}^{0}\rightarrow D^{+}h^{-}(h=K/\pi) signal distributions are represented by the sum of a double Gaussian function and an asymmetric Gaussian with a common mean. These signal probability density functions (PDFs) are common to both kaon- and pion-enhanced samples. The means of the signal PDFs for B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} and B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} are directly extracted from the data, along with a single scaling factor to the narrowest signal Gaussian to account for any difference in ΔE\Delta E resolution between simulated and data samples. Other parameters are fixed to those obtained from a fit to a large simulated sample of signal events.

A combined PDF is used to model combinatorial background consisting of continuum background and BB¯B\overline{B} background for B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} (B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-}) decay, where the continuum is modeled with a first-order polynomial and the combinatorial BB¯B\overline{B} background with an exponential function. The slope of the linear background and the exponential function’s exponent are determined from the fit to data; other parameters are fixed to those obtained from a fit to the corresponding simulated sample.

The cross feed background is described by a double Gaussian function in the B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} (B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-}) sample. The mean and scale factor for the B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} cross feed component PDF in the kaon-enhanced B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} sample are determined from the fit to data.

There is a background that can peak in the same manner as the B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} signal mode, which we call the “peaking background”. The most prominent decay that peaks in the ΔE\Delta E distribution is B0KJ/ψ,KK+π,J/ψμ+μB^{0}\rightarrow K^{*}J/\psi,K^{*}\rightarrow K^{+}\pi^{-},J/\psi\rightarrow\mu^{+}\mu^{-} or e+ee^{+}e^{-}. This source accounts for \sim2%\% of the total background. To reject this contamination arising due to leptons misidentified as pions, we veto candidates with an invariant mass M(π+π)M(\pi^{+}\pi^{-}) value falling within ±3σ\pm 3\sigma of the known J/ψJ/\psi mass cite-PDG . This essentially removes this peaking background with \sim3%\% signal loss. The remaining peaking background contributions include semileptonic DD decays for which the normalization is fixed from MC simulation. All yields are determined from a fit to data except for the peaking background yield. The uncertainty associated with the fixed peaking component is included in the systematic uncertainties. All other shape parameters are fixed to their MC values. The yields obtained from the fit are listed in Table 1, and the signal-enhanced fit projections for the data are shown in Fig. 2.

Table 1: Various event yields and their statistical uncertainties obtained from the simultaneous fit.
Parameter         Fit value
B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} total yield 42065±23542065\pm 235
B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} background yield 7414±1287414\pm 128
B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} background yield 2458±892458\pm 89
Refer to caption
Refer to caption
Figure 2: ΔE\Delta E distributions for B¯0D+h\overline{B}{}^{0}\rightarrow D^{+}h^{-} candidates obtained from the (left) pion-enriched B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} and (right) kaon-enriched B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} data samples. The projections of the combined fit and individual components of a simultaneous unbinned maximum-likelihood fit are overlaid. The long-dashed red curve shows the B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} component. The large-dotted magenta curve shows the B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} component. The small-dotted gray curve shows the combinatorial background component and the dash-dotted green curve show the peaking background component in B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} decay. The distribution of pulls between the fit and the data points is also shown.

V RESULTS

The branching fraction of B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} decay is calculated as,

(B¯0D+π)=\displaystyle\mathcal{B}(\overline{B}{}^{0}\rightarrow D^{+}\pi^{-})=
ND+πtotal2×f00×NBB¯×ϵD+π×(D+Kπ+π+),\displaystyle\frac{N^{\rm total}_{D^{+}\pi^{-}}}{2\times f_{00}\times N_{B\overline{B}}\times\epsilon_{D^{+}\pi^{-}}\times\mathcal{B}(D^{+}\rightarrow K^{-}\pi^{+}\pi^{+})}, (8)

where ND+πtotalN^{\rm total}_{D^{+}\pi^{-}} is the yield of B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} obtained from the fit, NBB¯N_{B\overline{B}} is the total number of BB¯B\overline{B} pairs, ϵD+π=(24.09±0.04)%\epsilon_{D^{+}\pi^{-}}=(24.09\pm 0.04)\% is the detection efficiency for B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} determined from signal MC events where the error is the associated statistical error from MC sample. The factor f00f_{00} represents the neutral BB meson production ratio at the Υ(4S)\Upsilon(4S), which is 0.486±0.0060.486\pm 0.006 cite-PDG , and (D+Kπ+π+)\mathcal{B}(D^{+}\rightarrow K^{-}\pi^{+}\pi^{+}) is the subdecay branching fraction of D+D^{+}, which is (9.38±0.16)%(9.38\pm 0.16)\% cite-PDG . The branching fraction for B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} decay is calculated by multiplying the RDR^{D} value from the fit by the calculated B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} branching fraction.

The systematic uncertainties in the measurements from various sources are listed in Table 2. Since the kinematics of B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} and B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} processes are similar, most of the systematic effects cancel in the ratio of their branching fractions. The main source of systematic uncertainty that does not cancel is the uncertainty in K/πK/\pi identification efficiency. All the sources of systematic uncertainty are assumed to be independent, such that the total uncertainty is the quadratic sum of their contributions. The uncertainty associated with the D+Kπ+π+D^{+}\rightarrow K^{-}\pi^{+}\pi^{+} subdecay branching fraction is taken from its world average cite-PDG . The uncertainty due to prompt tracking efficiency is based on a previous study of high momentum (p>200MeV)(p>200~{}\rm MeV) tracks. Tracking efficiency is calculated as the ratio between partially and fully reconstructed D+D^{+} decays in data and MC events. The entry for NBB¯N_{B\overline{B}} represents the uncertainty in the total number of BB¯B\overline{B} events in data. Here f00f_{00} refers to the uncertainty due to (Υ(4S)B0B¯)0\mathcal{B}(\Upsilon(4S)\rightarrow B^{0}\overline{B}{}^{0}) branching fraction calculated from PDG 2020 cite-PDG along with the uncertainty due to isospin asymmetry calculated in cite-isospin . The efficiency variation due to the D+Kπ+π+D^{+}\rightarrow K^{-}\pi^{+}\pi^{+} model is evaluated by varying the model and adding a phase space component. The resulting difference with respect to the measured central value of the branching fraction is treated as a systematic uncertainty. The systematic uncertainty due to PDFs for the D+h(h=K/π)D^{+}h^{-}(h=K/\pi) components and the D+h(h=K/π)D^{+}h^{-}(h=K/\pi) cross feed components are evaluated by varying the fixed shape parameters by ±1σ\pm 1\sigma. The uncertainty due to the kaon identification efficiency is calculated by varying the measured value by its uncertainty obtained in data from the DD^{*} calibration sample as described in Sec. III. The DD mass window and M(π+π)M(\pi^{+}\pi^{-}) for veto position have been varied and the resulting difference with respect to the measured branching fraction is taken as a systematic. The uncertainty due to the peaking background is obtained by varying its yield by the statistical uncertainty in its estimation. The uncertainty associated with the reconstruction efficiency is measured using signal MC data samples. We perform tests to validate the fit procedure and determine any possible bias in the fit procedure. The bias is not corrected and is used as a systematic uncertainty. The uncertainty due to the continuum suppression requirement is found to be negligible.

Table 2: Systematic uncertainties in the measured RDR^{D} value and branching fractions for B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} and B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-}. The total systematic uncertainty is the quadratic sum of the uncorrelated uncertainties.
Source     RDR^{D}     (B¯0D+π)\mathcal{B}(\overline{B}{}^{0}\rightarrow D^{+}\pi^{-})      (B¯0D+K)\mathcal{B}(\overline{B}{}^{0}\rightarrow D^{+}K^{-})
(D+Kπ+π+)\mathcal{B}(D^{+}\rightarrow K^{-}\pi^{+}\pi^{+}) 1.71%\% 1.71%\%
Tracking 1.40%\% 1.40%\%
NBB¯N_{B\overline{B}} 1.37%\% 1.37%\%
f00/f+f^{00}/f^{+-} 1.92%\% 1.92%\%
D+Kπ+π+D^{+}\rightarrow K^{-}\pi^{+}\pi^{+} model 0.69%0.69\% 0.69%0.69\%
PDF parametrization 2.71%2.71\% 1.63%\% 1.79%1.79\%
PID efficiency of K/πK/\pi 0.88%0.88\% 0.68%0.68\% 0.73%0.73\%
D+D^{+} mass selection window 0.05%0.05\% 0.56%\% 0.64%0.64\%
J/ψJ/\psi veto selection 0.12%0.12\% 0.004%\% 0.15%0.15\%
Peaking background yield 0.07%0.07\% 0.04%\% 0.00%0.00\%
MC statistics <0.01<0.01 0.04%\% 0.04%\%
Fit bias 0.58%\% 0.61%0.61\%
Total 2.85%2.85\% 3.43%3.43\% 3.54%3.54\%

The ratio of branching fractions is found to be,

RD\displaystyle R^{D} =\displaystyle= 0.0819±0.0020(stat)±0.0023(syst).\displaystyle 0.0819\pm 0.0020(\rm stat)\pm 0.0023(\rm syst). (9)

The total D+πD^{+}\pi^{-} yield from the simultaneous fit is used to determine the branching fraction of the B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} decay,

(B¯0D+π)\displaystyle\mathcal{B}(\overline{B}{}^{0}\rightarrow D^{+}\pi^{-}) =(2.48±0.01±0.09±0.04)×103\displaystyle=(2.48\pm 0.01\pm 0.09\pm 0.04)\times 10^{-3}
(10)

where the first uncertainty is statistical, the second is systematic, and the third is associated with D+Kπ+π+D^{+}\rightarrow K^{-}\pi^{+}\pi^{+} branching fraction. The branching fraction of B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} is calculated by multiplying Eq. (9) by Eq. (10),

(B¯0D+K)=(2.03±0.05±0.07±0.03)×104\mathcal{B}(\overline{B}{}^{0}\rightarrow D^{+}K^{-})=(2.03\pm 0.05\pm 0.07\pm 0.03)\times 10^{-4} (11)

The κ\kappa value obtained from the fit is (7.79±0.21)%(7.79\pm 0.21)\%, which agrees within one standard deviations with the expected pion misidentification rate as given in Sec. III. In both measurements listed in Eqs. (10) and (11), one of the dominant sources of systematic uncertainty arises from the fixed PDF parametrization.

VI Conclusion

In summary, we have reported measurements of the branching fraction ratio between Cabibbo suppressed B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} and Cabibbo favored B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} using the full Υ(4S)\Upsilon(4S) data sample collected by the Belle experiment, which supersedes the previous Belle measurement cite-belleold . We also present a measurement of the branching fractions for B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} and B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} decays.The B¯0D+h(h=K/π)\overline{B}{}^{0}\rightarrow D^{+}h^{-}(h=K/\pi) branching fraction and RDR^{D} values are compatible with the corresponding world averages cite-PDG within their uncertainties. Individual branching fractions of B¯0D+π\overline{B}{}^{0}\rightarrow D^{+}\pi^{-} and B¯0D+K\overline{B}{}^{0}\rightarrow D^{+}K^{-} deviate from the theory predictions in Refs. cite-arXix1606.02888 ; cite-arXiv:2007.10338 , however, the ratio agrees within uncertainties.

Acknowledgements

We thank the KEKB group for the excellent operation of the accelerator; the KEK cryogenics group for the efficient operation of the solenoid; and the KEK computer group, and the Pacific Northwest National Laboratory (PNNL) Environmental Molecular Sciences Laboratory (EMSL) computing group for strong computing support; and the National Institute of Informatics, and Science Information NETwork 5 (SINET5) for valuable network support. We acknowledge support from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan, the Japan Society for the Promotion of Science (JSPS), and the Tau-Lepton Physics Research Center of Nagoya University; the Australian Research Council including Grants No. DP180102629, No. DP170102389, No. DP170102204, No. DP150103061, and No. FT130100303; Austrian Federal Ministry of Education, Science and Research (FWF) and FWF Austrian Science Fund No. P 31361-N36; the National Natural Science Foundation of China under Contracts No. 11435013, No. 11475187, No. 11521505, No. 11575017, No. 11675166, and No. 11705209; Key Research Program of Frontier Sciences, Chinese Academy of Sciences (CAS), Grant No. QYZDJ-SSW-SLH011; the CAS Center for Excellence in Particle Physics (CCEPP); the Shanghai Science and Technology Committee (STCSM) under Grant No. 19ZR1403000; the Ministry of Education, Youth and Sports of the Czech Republic under Contract No. LTT17020; Horizon 2020 ERC Advanced Grant No. 884719 and ERC Starting Grant No. 947006 “InterLeptons” (European Union); the Carl Zeiss Foundation, the Deutsche Forschungsgemeinschaft, the Excellence Cluster Universe, and the VolkswagenStiftung; the Department of Atomic Energy (Project Identification No. RTI 4002) and the Department of Science and Technology of India; the Istituto Nazionale di Fisica Nucleare of Italy; National Research Foundation (NRF) of Korea Grants No. 2016R1D1A1B01010135, No. 2016R1D1A1B02012900, No. 2018R1A2B3003643, No. 2018R1A6A1A06024970, No. 2019K1A3A7A09033840, No. 2019R1I1A3A01058933, No. 2021R1A6A1A03043957, No. 2021R1F1A1060423, No. 2021R1F1A1064008; Radiation Science Research Institute, Foreign Large-size Research Facility Application Supporting project, the Global Science Experimental Data Hub Center of the Korea Institute of Science and Technology Information and KREONET/GLORIAD; the Polish Ministry of Science and Higher Education and the National Science Center; the Ministry of Science and Higher Education of the Russian Federation, Agreement 14.W03.31.0026, and the HSE University Basic Research Program, Moscow; University of Tabuk research Grants No. S-1440-0321, No. S-0256-1438, and No. S-0280-1439 (Saudi Arabia); the Slovenian Research Agency Grants No. J1-9124 and No. P1-0135; Ikerbasque, Basque Foundation for Science, Spain; the Swiss National Science Foundation; the Ministry of Education and the Ministry of Science and Technology of Taiwan; and the United States Department of Energy and the National Science Foundation.

References

  • (1) M. Neubert and A. A. Petrov, Phys. Lett. B 519, 50 (2001).
  • (2) R. Fleischer, N. Serra, and N. Tuning, Phys. Rev. D 83, 014017 (2011).
  • (3) K. Abe et al., (Belle Collaboration), Phys. Rev. Lett. 87, 111801 (2001).
  • (4) M. Neubert and B. Stech, Adv. Ser. Direct. High Energy Phys. 15, 294 (1998).
  • (5) M. Beneke, G. Buchalla, M. Neubert, and C. T. Sachrajda, Nucl. Phys. B 591, 313 (2000).
  • (6) T. Huber, S. Kränkl, and X.-Q. Li, J. High Energ. Phys. 09, 112 (2016).
  • (7) M. Bordone, N. Gubernari, T. Huber, M. Jung, and D. van Dyk, Eur. Phys. J. C 80, 951 (2020).
  • (8) N. Cabibbo, Phys. Rev. Lett. 10, 531 (1963); M. Kobayashi and K. Maskawa, Prog. Theor. Phys. 49, 652 (1973).
  • (9) F.-M. Cai, W.-J. Deng, X.-Q. Li, and Y.-D. Yang, J. High 567 Energy Phys. 10 (2021) 235.
  • (10) R. Fleischer and E. Malami, arXiv:2109.04950.
  • (11) S. Iguro and T. Kitahara, Phys. Rev. D 102, 071701(R) (2020).
  • (12) M. Endo, S. Iguro, and S. Mishima, arXiv:2109.10811.
  • (13) B. Aubert et al. (BABAR Collaboration), Phys. Rev. D 74, 111102 (2006).
  • (14) B. Aubert et al. (BABAR Collaboration), Phys. Rev. D 75, 031101 (2007).
  • (15) D. Bortoletto et al. (CLEO Collaboration), Phys. Rev. D 45, 21 (1992).
  • (16) S. Ahmed et al. (CLEO Collaboration), Phys. Rev. D 66, 031101 (2002).
  • (17) H. Albrecht et al. (ARGUS Collaboration), Z. Phys. C 54, 1 (1992).
  • (18) R. Aaij et al. (LHCb Collaboration), Phys. Rev. Lett 107, 211801 (2011).
  • (19) P. A. Zyla et al. (Particle Data Group), Prog. Theor. Exp. Phys. 2020, 083C01 (2020).
  • (20) R. Aaij et al. (LHCb Collaboration), J. High Energ. Phys. 04, 001 (2013).
  • (21) A. Abashian et al. (Belle Collaboration), Nucl. Instrum. Methods Phys. Res., Sect. A 479, 117 (2002); also see Section 2 in J. Brodzicka et al., Prog. Theor. Exp. Phys. 2012, 04D001 (2012).
  • (22) S. Kurokawa and E. Kikutani, Nucl. Instrum. Methods Phys. Res., Sect. A 499, 1 (2003), and other papers included in this Volume; T. Abe et al., Prog. Theor. Exp. Phys. 2013, 03A001 (2013) and references therein.
  • (23) D. J. Lange, Nucl. Instrum. Methods. Phys. Res., Sec. A 462, 152 (2001).
  • (24) E. Barberio, B. van Eijk, and Z. Was, Comput. Phys. Commun. 66 (1991) 115.
  • (25) R. Brun et al., GEANT 3.21, CERN Report DD/EE/84-1, 1984.
  • (26) T. Kuhr et al. (Belle II Framework Software Group), Comput. Softw. Big Sci. 3, 1 (2019).
  • (27) M. Gelb et al., Comput. Softw. Big Sci. 2, 9 (2018).
  • (28) G. C. Fox and S. Wolfram, Phys. Rev. Lett. 41, 1581 (1978).
  • (29) S. Choudhury et al., (Belle Collaboration), J. High Energ. Phys. 03, (2021) 105.