Observation of $B^{+} \rightarrow p\barΛ K^+ K^-$ and $B^{+} \rightarrow \bar{p}ΛK^+ K^+$
P. -C. Lu M. -Z. Wang R. Chistov P. Chang I. Adachi J. K. Ahn H. Aihara S. Al Said D. M. Asner H. Atmacan V. Aulchenko T. Aushev R. Ayad V. Babu I. Badhrees A. M. Bakich V. Bansal P. Behera C. Beleno M. Berger V. Bhardwaj B. Bhuyan T. Bilka J. Biswal G. Bonvicini A. Bozek M. Bračko T. E. Browder L. Cao D. Červenkov V. Chekelian A. Chen B. G. Cheon K. Chilikin K. Cho S. -K. Choi Y. Choi S. Choudhury D. Cinabro S. Cunliffe N. Dash S. Di Carlo Z. Doležal T. V. Dong Z. Drásal S. Eidelman D. Epifanov J. E. Fast T. Ferber B. G. Fulsom R. Garg V. Gaur N. Gabyshev A. Garmash M. Gelb A. Giri P. Goldenzweig E. Guido J. Haba K. Hayasaka H. Hayashii S. Hirose W. -S. Hou C. -L. Hsu T. Iijima K. Inami G. Inguglia A. Ishikawa R. Itoh M. Iwasaki Y. Iwasaki W. W. Jacobs H. B. Jeon S. Jia Y. Jin D. Joffe K. K. Joo T. Julius A. B. Kaliyar T. Kawasaki H. Kichimi C. Kiesling D. Y. Kim H. J. Kim J. B. Kim K. T. Kim S. H. Kim K. Kinoshita P. Kodyš S. Korpar D. Kotchetkov P. Križan R. Kroeger P. Krokovny T. Kuhr R. Kulasiri A. Kuzmin Y. -J. Kwon Y. -T. Lai J. S. Lange I. S. Lee S. C. Lee L. K. Li Y. B. Li L. Li Gioi J. Libby D. Liventsev M. Lubej T. Luo M. Masuda T. Matsuda D. Matvienko M. Merola K. Miyabayashi H. Miyata R. Mizuk G. B. Mohanty H. K. Moon T. Mori R. Mussa M. Nakao T. Nanut K. J. Nath Z. Natkaniec M. Nayak N. K. Nisar S. Nishida S. Ogawa S. Okuno H. Ono H. Ozaki P. Pakhlov G. Pakhlova B. Pal S. Pardi H. Park S. Paul T. K. Pedlar R. Pestotnik L. E. Piilonen V. Popov E. Prencipe A. Rabusov M. Ritter A. Rostomyan G. Russo Y. Sakai M. Salehi S. Sandilya L. Santelj T. Sanuki V. Savinov O. Schneider G. Schnell C. Schwanda Y. Seino K. Senyo M. E. Sevior V. Shebalin C. P. Shen T. -A. Shibata J. -G. Shiu B. Shwartz F. Simon J. B. Singh A. Sokolov E. Solovieva M. Starič J. F. Strube M. Sumihama T. Sumiyoshi W. Sutcliffe M. Takizawa U. Tamponi K. Tanida F. Tenchini M. Uchida T. Uglov Y. Unno S. Uno P. Urquijo Y. Usov S. E. Vahsen C. Van Hulse R. Van Tonder G. Varner A. Vinokurova V. Vorobyev A. Vossen B. Wang C. H. Wang M. Watanabe S. Watanuki E. Widmann E. Won H. Ye J. H. Yin C. Z. Yuan Z. P. Zhang V. Zhilich V. Zhukova V. Zhulanov A. Zupanc








   Belle Preprint 2018-15
                   KEK Preprint 2018-21
















University of the Basque Country UPV/EHU, 48080 Bilbao
Beihang University, Beijing 100191

Brookhaven National Laboratory, Upton, New York 11973
Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090
Faculty of Mathematics and Physics, Charles University, 121 16 Prague

Chonnam National University, Kwangju 660-701
University of Cincinnati, Cincinnati, Ohio 45221
Deutsches Elektronen–Synchrotron, 22607 Hamburg
Duke University, Durham, North Carolina 27708


Key Laboratory of Nuclear Physics and Ion-beam Application (MOE) and Institute of Modern Physics, Fudan University, Shanghai 200443
Justus-Liebig-Universität Gießen, 35392 Gießen
Gifu University, Gifu 501-1193
II. Physikalisches Institut, Georg-August-Universität Göttingen, 37073 Göttingen
SOKENDAI (The Graduate University for Advanced Studies), Hayama 240-0193
Gyeongsang National University, Chinju 660-701
Hanyang University, Seoul 133-791
University of Hawaii, Honolulu, Hawaii 96822
High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801
J-PARC Branch, KEK Theory Center, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801
Forschungszentrum Jülich, 52425 Jülich

IKERBASQUE, Basque Foundation for Science, 48013 Bilbao

Indian Institute of Science Education and Research Mohali, SAS Nagar, 140306
Indian Institute of Technology Bhubaneswar, Satya Nagar 751007
Indian Institute of Technology Guwahati, Assam 781039
Indian Institute of Technology Hyderabad, Telangana 502285
Indian Institute of Technology Madras, Chennai 600036
Indiana University, Bloomington, Indiana 47408
Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049
Institute of High Energy Physics, Vienna 1050
Institute for High Energy Physics, Protvino 142281

INFN - Sezione di Napoli, 80126 Napoli
INFN - Sezione di Torino, 10125 Torino
Advanced Science Research Center, Japan Atomic Energy Agency, Naka 319-1195
J. Stefan Institute, 1000 Ljubljana
Kanagawa University, Yokohama 221-8686
Institut für Experimentelle Teilchenphysik, Karlsruher Institut für Technologie, 76131 Karlsruhe

Kennesaw State University, Kennesaw, Georgia 30144
King Abdulaziz City for Science and Technology, Riyadh 11442
Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah 21589

Korea Institute of Science and Technology Information, Daejeon 305-806
Korea University, Seoul 136-713

Kyungpook National University, Daegu 702-701
LAL, Univ. Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, Orsay
École Polytechnique Fédérale de Lausanne (EPFL), Lausanne 1015
P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991
Faculty of Mathematics and Physics, University of Ljubljana, 1000 Ljubljana
Ludwig Maximilians University, 80539 Munich
Luther College, Decorah, Iowa 52101
University of Malaya, 50603 Kuala Lumpur
University of Maribor, 2000 Maribor
Max-Planck-Institut für Physik, 80805 München
School of Physics, University of Melbourne, Victoria 3010
University of Mississippi, University, Mississippi 38677
University of Miyazaki, Miyazaki 889-2192
Moscow Physical Engineering Institute, Moscow 115409
Moscow Institute of Physics and Technology, Moscow Region 141700
Graduate School of Science, Nagoya University, Nagoya 464-8602
Kobayashi-Maskawa Institute, Nagoya University, Nagoya 464-8602
Università di Napoli Federico II, 80055 Napoli

Nara Women's University, Nara 630-8506
National Central University, Chung-li 32054
National United University, Miao Li 36003
Department of Physics, National Taiwan University, Taipei 10617
H. Niewodniczanski Institute of Nuclear Physics, Krakow 31-342
Nippon Dental University, Niigata 951-8580
Niigata University, Niigata 950-2181

Novosibirsk State University, Novosibirsk 630090
Osaka City University, Osaka 558-8585

Pacific Northwest National Laboratory, Richland, Washington 99352
Panjab University, Chandigarh 160014
Peking University, Beijing 100871
University of Pittsburgh, Pittsburgh, Pennsylvania 15260



Theoretical Research Division, Nishina Center, RIKEN, Saitama 351-0198


University of Science and Technology of China, Hefei 230026


Showa Pharmaceutical University, Tokyo 194-8543
Soongsil University, Seoul 156-743
University of South Carolina, Columbia, South Carolina 29208
Stefan Meyer Institute for Subatomic Physics, Vienna 1090
Sungkyunkwan University, Suwon 440-746
School of Physics, University of Sydney, New South Wales 2006
Department of Physics, Faculty of Science, University of Tabuk, Tabuk 71451
Tata Institute of Fundamental Research, Mumbai 400005
Excellence Cluster Universe, Technische Universität München, 85748 Garching
Department of Physics, Technische Universität München, 85748 Garching
Toho University, Funabashi 274-8510

Department of Physics, Tohoku University, Sendai 980-8578
Earthquake Research Institute, University of Tokyo, Tokyo 113-0032
Department of Physics, University of Tokyo, Tokyo 113-0033
Tokyo Institute of Technology, Tokyo 152-8550
Tokyo Metropolitan University, Tokyo 192-0397


Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061
Wayne State University, Detroit, Michigan 48202
Yamagata University, Yamagata 990-8560
Yonsei University, Seoul 120-749

  Department of Physics, National Taiwan University, Taipei 10617 
  Department of Physics, National Taiwan University, Taipei 10617 
  P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991Moscow Physical Engineering Institute, Moscow 115409 
  Department of Physics, National Taiwan University, Taipei 10617 
  High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801SOKENDAI (The Graduate University for Advanced Studies), Hayama 240-0193 

  Korea University, Seoul 136-713 
  Department of Physics, University of Tokyo, Tokyo 113-0033 
  Department of Physics, Faculty of Science, University of Tabuk, Tabuk 71451Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah 21589 


  Brookhaven National Laboratory, Upton, New York 11973 
  University of South Carolina, Columbia, South Carolina 29208 
  Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090Novosibirsk State University, Novosibirsk 630090 
  Moscow Institute of Physics and Technology, Moscow Region 141700 
  Department of Physics, Faculty of Science, University of Tabuk, Tabuk 71451 

  Tata Institute of Fundamental Research, Mumbai 400005 
  Department of Physics, Faculty of Science, University of Tabuk, Tabuk 71451King Abdulaziz City for Science and Technology, Riyadh 11442 

  School of Physics, University of Sydney, New South Wales 2006 

  Pacific Northwest National Laboratory, Richland, Washington 99352 



  Indian Institute of Technology Madras, Chennai 600036 
  II. Physikalisches Institut, Georg-August-Universität Göttingen, 37073 Göttingen 

  Stefan Meyer Institute for Subatomic Physics, Vienna 1090 


  Indian Institute of Science Education and Research Mohali, SAS Nagar, 140306 
  Indian Institute of Technology Guwahati, Assam 781039 
  Faculty of Mathematics and Physics, Charles University, 121 16 Prague 
  J. Stefan Institute, 1000 Ljubljana 



  Wayne State University, Detroit, Michigan 48202 
  H. Niewodniczanski Institute of Nuclear Physics, Krakow 31-342 
  University of Maribor, 2000 MariborJ. Stefan Institute, 1000 Ljubljana 



  University of Hawaii, Honolulu, Hawaii 96822 
  Institut für Experimentelle Kernphysik, Karlsruher Institut für Technologie, 76131 Karlsruhe 

  Faculty of Mathematics and Physics, Charles University, 121 16 Prague 



  Max-Planck-Institut für Physik, 80805 München 
  National Central University, Chung-li 32054 

  Hanyang University, Seoul 133-791 
  P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991 
  Korea Institute of Science and Technology Information, Daejeon 305-806 

  Gyeongsang National University, Chinju 660-701 
  Sungkyunkwan University, Suwon 440-746 
  Indian Institute of Technology Hyderabad, Telangana 502285 
  Wayne State University, Detroit, Michigan 48202 

  Deutsches Elektronen–Synchrotron, 22607 Hamburg 


  Indian Institute of Technology Bhubaneswar, Satya Nagar 751007 
  LAL, Univ. Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, Orsay 

  Faculty of Mathematics and Physics, Charles University, 121 16 Prague 
  High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801SOKENDAI (The Graduate University for Advanced Studies), Hayama 240-0193 

  Faculty of Mathematics and Physics, Charles University, 121 16 Prague 



  Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090Novosibirsk State University, Novosibirsk 630090P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991 
  Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090Novosibirsk State University, Novosibirsk 630090 
  Pacific Northwest National Laboratory, Richland, Washington 99352 

  Deutsches Elektronen–Synchrotron, 22607 Hamburg 


  Pacific Northwest National Laboratory, Richland, Washington 99352 
  Panjab University, Chandigarh 160014 
  Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 
  Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090Novosibirsk State University, Novosibirsk 630090 
  Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090Novosibirsk State University, Novosibirsk 630090 
  Institut für Experimentelle Kernphysik, Karlsruher Institut für Technologie, 76131 Karlsruhe 



  Indian Institute of Technology Hyderabad, Telangana 502285 


  Institut für Experimentelle Kernphysik, Karlsruher Institut für Technologie, 76131 Karlsruhe 






  INFN - Sezione di Torino, 10125 Torino 

  High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801SOKENDAI (The Graduate University for Advanced Studies), Hayama 240-0193 





  Niigata University, Niigata 950-2181 
  Nara Women's University, Nara 630-8506 







  Graduate School of Science, Nagoya University, Nagoya 464-8602 



  Department of Physics, National Taiwan University, Taipei 10617 

  School of Physics, University of Melbourne, Victoria 3010 


  Kobayashi-Maskawa Institute, Nagoya University, Nagoya 464-8602Graduate School of Science, Nagoya University, Nagoya 464-8602 

  Graduate School of Science, Nagoya University, Nagoya 464-8602 
  Deutsches Elektronen–Synchrotron, 22607 Hamburg 
  Department of Physics, Tohoku University, Sendai 980-8578 

  High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801SOKENDAI (The Graduate University for Advanced Studies), Hayama 240-0193 
  Osaka City University, Osaka 558-8585 
  High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801 

  Indiana University, Bloomington, Indiana 47408 

  Kyungpook National University, Daegu 702-701 
  Beihang University, Beijing 100191 
  Department of Physics, University of Tokyo, Tokyo 113-0033 
  Kennesaw State University, Kennesaw, Georgia 30144 

  Chonnam National University, Kwangju 660-701 
  School of Physics, University of Melbourne, Victoria 3010 


  Indian Institute of Technology Madras, Chennai 600036 









  Niigata University, Niigata 950-2181 

  High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801 
  Max-Planck-Institut für Physik, 80805 München 

  Soongsil University, Seoul 156-743 
  Kyungpook National University, Daegu 702-701 

  Korea University, Seoul 136-713 
  Korea University, Seoul 136-713 
  Hanyang University, Seoul 133-791 




  University of Cincinnati, Cincinnati, Ohio 45221 



  Faculty of Mathematics and Physics, Charles University, 121 16 Prague 


  University of Maribor, 2000 MariborJ. Stefan Institute, 1000 Ljubljana 
  University of Hawaii, Honolulu, Hawaii 96822 

  Faculty of Mathematics and Physics, University of Ljubljana, 1000 LjubljanaJ. Stefan Institute, 1000 Ljubljana 
  University of Mississippi, University, Mississippi 38677 

  Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090Novosibirsk State University, Novosibirsk 630090 

  Ludwig Maximilians University, 80539 Munich 
  Kennesaw State University, Kennesaw, Georgia 30144 




  Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090Novosibirsk State University, Novosibirsk 630090 

  Yonsei University, Seoul 120-749 
  High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801 
  Justus-Liebig-Universität Gießen, 35392 Gießen 
  Hanyang University, Seoul 133-791 
  Kyungpook National University, Daegu 702-701 






  Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 

  Peking University, Beijing 100871 
  Max-Planck-Institut für Physik, 80805 München 
  Indian Institute of Technology Madras, Chennai 600036 



  Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801 



  J. Stefan Institute, 1000 Ljubljana 
  Key Laboratory of Nuclear Physics and Ion-beam Application (MOE) and Institute of Modern Physics, Fudan University, Shanghai 200443 


  Earthquake Research Institute, University of Tokyo, Tokyo 113-0032 
  University of Miyazaki, Miyazaki 889-2192 
  Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090Novosibirsk State University, Novosibirsk 630090P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991 


  INFN - Sezione di Napoli, 80126 NapoliUniversità di Napoli Federico II, 80055 Napoli 


  Nara Women's University, Nara 630-8506 


  Niigata University, Niigata 950-2181 

  P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991Moscow Physical Engineering Institute, Moscow 115409Moscow Institute of Physics and Technology, Moscow Region 141700 
  Tata Institute of Fundamental Research, Mumbai 400005 

  Korea University, Seoul 136-713 
  Graduate School of Science, Nagoya University, Nagoya 464-8602 





  INFN - Sezione di Torino, 10125 Torino 







  High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801SOKENDAI (The Graduate University for Advanced Studies), Hayama 240-0193 


  J. Stefan Institute, 1000 Ljubljana 
  Indian Institute of Technology Guwahati, Assam 781039 
  H. Niewodniczanski Institute of Nuclear Physics, Krakow 31-342 
  Wayne State University, Detroit, Michigan 48202High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801 




  University of Pittsburgh, Pittsburgh, Pennsylvania 15260 
  High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801SOKENDAI (The Graduate University for Advanced Studies), Hayama 240-0193 



  Toho University, Funabashi 274-8510 

  Kanagawa University, Yokohama 221-8686 

  Nippon Dental University, Niigata 951-8580Niigata University, Niigata 950-2181 




  High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801SOKENDAI (The Graduate University for Advanced Studies), Hayama 240-0193 
  P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991Moscow Physical Engineering Institute, Moscow 115409 
  P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991Moscow Institute of Physics and Technology, Moscow Region 141700 
  Brookhaven National Laboratory, Upton, New York 11973 


  INFN - Sezione di Napoli, 80126 Napoli 


  Kyungpook National University, Daegu 702-701 

  Department of Physics, Technische Universität München, 85748 Garching 

  Luther College, Decorah, Iowa 52101 


  J. Stefan Institute, 1000 Ljubljana 

  Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 

  P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991Moscow Institute of Physics and Technology, Moscow Region 141700 

  Forschungszentrum Jülich, 52425 Jülich 



  Department of Physics, Technische Universität München, 85748 Garching 




  Ludwig Maximilians University, 80539 Munich 

  Deutsches Elektronen–Synchrotron, 22607 Hamburg 


  INFN - Sezione di Napoli, 80126 Napoli 



  High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801SOKENDAI (The Graduate University for Advanced Studies), Hayama 240-0193 
  University of Malaya, 50603 Kuala LumpurLudwig Maximilians University, 80539 Munich 
  University of Cincinnati, Cincinnati, Ohio 45221 

  High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801 
  Department of Physics, Tohoku University, Sendai 980-8578 



  University of Pittsburgh, Pittsburgh, Pennsylvania 15260 

  École Polytechnique Fédérale de Lausanne (EPFL), Lausanne 1015 
  University of the Basque Country UPV/EHU, 48080 BilbaoIKERBASQUE, Basque Foundation for Science, 48013 Bilbao 


  Institute of High Energy Physics, Vienna 1050 



  Niigata University, Niigata 950-2181 

  Yamagata University, Yamagata 990-8560 


  School of Physics, University of Melbourne, Victoria 3010 


  Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090Novosibirsk State University, Novosibirsk 630090 
  Beihang University, Beijing 100191 
  Tokyo Institute of Technology, Tokyo 152-8550 


  Department of Physics, National Taiwan University, Taipei 10617 
  Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090Novosibirsk State University, Novosibirsk 630090 

  Max-Planck-Institut für Physik, 80805 MünchenExcellence Cluster Universe, Technische Universität München, 85748 Garching 
  Panjab University, Chandigarh 160014 

  Institute for High Energy Physics, Protvino 142281 

  P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991Moscow Institute of Physics and Technology, Moscow Region 141700 

  J. Stefan Institute, 1000 Ljubljana 


  Pacific Northwest National Laboratory, Richland, Washington 99352 



  Gifu University, Gifu 501-1193 

  Tokyo Metropolitan University, Tokyo 192-0397 
  Institut für Experimentelle Kernphysik, Karlsruher Institut für Technologie, 76131 Karlsruhe 






  Showa Pharmaceutical University, Tokyo 194-8543J-PARC Branch, KEK Theory Center, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801Theoretical Research Division, Nishina Center, RIKEN, Saitama 351-0198 
  INFN - Sezione di Torino, 10125 Torino 


  Advanced Science Research Center, Japan Atomic Energy Agency, Naka 319-1195 



  School of Physics, University of Melbourne, Victoria 3010 




  Tokyo Institute of Technology, Tokyo 152-8550 



  P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991Moscow Institute of Physics and Technology, Moscow Region 141700 
  Hanyang University, Seoul 133-791 
  High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801SOKENDAI (The Graduate University for Advanced Studies), Hayama 240-0193 
  School of Physics, University of Melbourne, Victoria 3010 

  Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090Novosibirsk State University, Novosibirsk 630090 
  University of Hawaii, Honolulu, Hawaii 96822 
  University of the Basque Country UPV/EHU, 48080 Bilbao 
  Institut für Experimentelle Kernphysik, Karlsruher Institut für Technologie, 76131 Karlsruhe 

  University of Hawaii, Honolulu, Hawaii 96822 


  Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090Novosibirsk State University, Novosibirsk 630090 
  Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090Novosibirsk State University, Novosibirsk 630090P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991 
  Duke University, Durham, North Carolina 27708 


  University of Cincinnati, Cincinnati, Ohio 45221 
  National United University, Miao Li 36003 
    Key Laboratory of Nuclear Physics and Ion-beam Application (MOE) and Institute of Modern Physics, Fudan University, Shanghai 200443 
  Niigata University, Niigata 950-2181 

  Department of Physics, Tohoku University, Sendai 980-8578 


  Stefan Meyer Institute for Subatomic Physics, Vienna 1090 


  Korea University, Seoul 136-713 





  Deutsches Elektronen–Synchrotron, 22607 Hamburg 

  Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 

  Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 




  University of Science and Technology of China, Hefei 230026 

  Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090Novosibirsk State University, Novosibirsk 630090 
  P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991Moscow Physical Engineering Institute, Moscow 115409 
  Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090Novosibirsk State University, Novosibirsk 630090 

  Faculty of Mathematics and Physics, University of Ljubljana, 1000 LjubljanaJ. Stefan Institute, 1000 Ljubljana 

The Belle Collaboration





We report the study of  and  decays using a 772 × 10^6 BB̅ pair data sample recorded on the Υ(4S) resonance with the Belle detector at KEKB. The following branching fractions are measured: ℬ() = (4.10^+0.45_-0.43± 0.50)×10^-6, ℬ() = (3.70^+0.39_-0.37± 0.44)× 10^-6, ℬ(+c.c.) = (2.83^+0.36_-0.34± 0.35)× 10^-3 and ℬ() = (7.95 ± 2.09 ± 0.77) × 10^-7, where c.c. denotes the corresponding charge-conjugation process. The intermediate resonance decays are excluded in the four-body decay measurements. We also find evidence for ℬ(+c.c.) = (3.48 ± 1.48 ± 0.46) × 10^-3 and ℬ() = (2.23 ± 0.63 ± 0.25) × 10^-6. No significant signals are found for +c.c. and ; we set the 90% confidence level upper limits on their decay branching fractions as < 1.80×10^-3 and < 2.08×10^-6, respectively.



13.25.Hw, 13.25.Ft, 13.25.Gv, 14.20.Gk,




Observation of B^+→ pΛ̅ K^+ K^- and B^+→p̅Λ K^+ K^+
    A. Zupanc
    December 30, 2023
===================================================



Baryonic B decays have been studied at the B-factories <cit.>, and many intriguing features have been found. Baryon-antibaryon pairs are produced almost
collinearly in most baryonic B decays such that their masses peak
near threshold. There seems to exist a hierarchical structure in the branching fractions of multi-body decays, e.g., ℬ(B^0 → pΛ̅^-_cπ^+π^-) > ℬ(B^+ → pΛ̅^-_cπ^+)
> ℬ(B^0 → pΛ̅^-_c) <cit.>[Through out this paper, inclusion of charge-conjugate mode is always implied if the charge-conjugate final states are not specifically mentioned together.]. The angular distribution of the proton against the energetic
meson (K^+ or π^- for the following cases) in the dibaryon system of B^+ → pp̅K^+ and B^0 → pΛ̅π^- show a trend opposit to those predicted by theory <cit.>. These two decays occur presumably via the b → s g penguin process, where g denotes a hard gluon.

Lately, many more interesting phenomena in baryonic B decays have been found by the LHCb experiment, for example,  very rare two-body decays like B^0 →  p p̅ <cit.>, first evidence for CP violation in baryonic B decays <cit.>, baryonic B_s decay <cit.>, baryonic B_c decay <cit.>, and many first observations of four-body B^0 and B_s decays <cit.>.

A generalized factorization picture <cit.> can qualitatively explain some of the experimental findings. However, the predicted branching fractions may differ by a factor of ten from experimental measurements, e.g., B^0 → p Λ̅ D^*-  <cit.>. Later theoretical predictions <cit.> better compare with data after using improved baryonic form factors. It is clear that further studies of baryonic B decays are needed in order to improve theoretical understanding. In this paper, we report measurements of  and , for which theoretical predictions of ℬ() <cit.> and ℬ() <cit.> are available.

The data sample used in this study corresponds to an integrated luminosity of  711 fb^-1,
which contains 772×10^6 BB̅ pairs produced at the Υ(4S) resonance.
The Belle detector <cit.> is located at the interaction point (IP) of
the  KEKB asymmetric-energy e^+ (3.5 GeV) e^- (8 GeV) collider <cit.>.
It is a large-solid-angle spectrometer comprising six specialized subdetectors:
the Silicon Vertex Detector, the 50-layer Central Drift Chamber (CDC),
the Aerogel Cherenkov Counter (ACC), the Time-Of-Flight scintillation counter (TOF),
the electromagnetic calorimeter (ECL), and the K_L^0 and muon detector (KLM).
A superconducting solenoid surrounding all but the KLM produces a 1.5 T magnetic field.

In this analysis, we combine pΛ̅ K^+ K^- (p̅Λ K^+ K^+) to form B^+ candidates. We require charged particles (tracks from Λ are excluded) to originate near the IP, less than 1.0 cm away along the positron beam direction and less than 0.2 cm away in the transverse plane. To identify a kaon or a proton track,
we use the likelihood information from the charged-hadron identification system (CDC, ACC, TOF) <cit.> and apply the same selection criteria as in Ref. <cit.>. We use information from ECL and KLM to reject charged particles resembling electrons and muons. We require Λ(pπ^-) candidates to have a displaced vertex that is consistent with a long-lived particle originating from the IP and a mass between 1.111 and 1.121 GeV/c^2.



We use the following two variables, Δ E ≡ E_ recon - E_ beam and M_ bc≡√((E_ beam/c^2)^2-(P_ recon/c)^2), to identify signal, where E_ recon/P_ recon and E_ beam are the reconstructed B energy/momentum and beam energy measured in the Υ(4S) rest frame, respectively. We define 5.24 < M_ bc < 5.29 GeV/c^2 and |Δ E| < 0.2 GeV as the fit region; 5.27 < M_ bc < 5.29 GeV/c^2 and |Δ E| < 0.03 GeV as the signal region.










The dominant background is from the continuum process (e^+e^- → qq̅, q=u,d,s,c).
We generate phase space  and  signal events and continuum background
using EvtGen <cit.> and later process them with a GEANT3-based detector simulation program
that provides the detector-level information <cit.>.
These Monte Carlo (MC) samples are used to optimize the signal selection criteria. We use a neural network
package, Neurobayes <cit.>, for background suppression. There are 21 input variables for the training of Neurobayes: 17 modified Fox-Wolfram moments treating the information of particles involved in the signal B candidate separately from those in the rest of the event <cit.> to distinguish spherical B B̅ events from the jet-like qq̅ events, the missing mass of each event, the vertex difference between the B^+ candidate and the accompanying B, the angle between B^+ flight direction and the beam axis in the Υ(4S) rest frame, and the tagging information for the accompanying B  <cit.>. The output value of Neurobayes is between +1 (BB̅-like) and -1 (qq̅-like). The optimized selection and its related systematic uncertainty is mode dependent.

We consider at most one B^+ candidate in each event: if there are multiple candidates, we select the one with the smallest (χ^2_B_ vtx+χ^2_Λ_ vtx), where χ^2_B(Λ)_vtx  represents the χ^2 value of B(Λ) vertex fit. The probability to have multiple B candidates is less than 6% and the success rate of this selection is larger than 92% according to MC study.

In the investigation of possible intermediate states in  and , we check the mass spectra from combinations of various final-state particles in and near the signal region. We find many intermediate resonances: η_c, J/ψ and χ_c1 in M(pΛ̅K^-); ϕ in M(K^+K^-); Λ(1520) in M(p K^-).
After removing events in the mass windows of resonances: 2.92 <M(pΛ̅K^-)< 3.11 GeV/c^2 for η_c and J/ψ, 3.49 <M(pΛ̅K^-)< 3.53 GeV/c^2 for χ_c1, 1.01 <M(K^+K^-)< 1.03 GeV/c^2 for ϕ, and 1.46 <M(pK^-)< 1.58 GeV/c^2 for Λ(1520),
we still observe a large number of signal events. We attribute them to genuine four-body decays. Note that there is no significant D^0 peak found. We also find a threshold peak mixed with the phase space distribution in the pΛ̅ mass spectrum. Therefore, we generate signal MC samples with this feature to mimic data. This mixing ratio is mode dependent in order to match with data.

We use an extended unbinned maximum likelihood fit to extract signal yields of genuine  and  four-body decays. The likelihood function is defined as


    ℒ=e^-(N_s+N_b)/N!∏_i=1^N (N_s P_s( ΔE^i, M_ bc^i) +N_b P_b(  ΔE^i, M_ bc^i)),

where N is the number of total events, i denotes the event index, N_s and N_b are fit parameters representing the numbers of signal events and background events, respectively; P_s and P_b are the probability density functions of signal and background, respectively.

Backgrounds like generic (b → c) B decays and other rare (b → u,d,s) B decays, after investigation of MC simulation, show no peak in the fit region. We combine them with continuum background as the general background to fit with. We use Gaussian functions to model the signal shapes in both Δ E and M_ bc, a second-order polynomial function for the background Δ E distribution and an ARGUS function <cit.> for the background M_ bc distribution. The fit results are displayed in Fig. <ref>. Note that the possible feed-down events from B^+ → pΣ̅^̅0̅K^+K^- and B^+ →p̅Σ^0 K^+K^+ will form a peak around -0.1 GeV in the ΔE spectra. The fit bias due to this excess around -0.1 GeV is negligible (<0.4%). We apply the same fitting procedure in bins of M_pΛ̅/p̅Λ to determine the signal yields. The corresponding normalized and efficiency-corrected signal yield distributions are shown in Fig. <ref>. Clear threshold peaks and non-negligible phase space contributions are observed.








Since the signal yield is significant enough, we fix the signal shapes in a similar likelihood fit to extract the signal yields with intermediate resonances η_c, J/ψ, χ_c1, Λ(1520) and ϕ. In addition to Δ E and  M_ bc, we include the invariant mass of an intermediate resonance as a third variable in our fit assuming that the probability density function, P(M_ res), is independent of P(Δ E, M_ bc). We use the world average mass and width values of these resonances to generate MC samples <cit.>. For η_c and ϕ, we use a Breit-Wigner function convolved with a Gaussian function; for J/ψ and χ_c1, we use the sum of two Gaussian functions in order to fit the corresponding MC mass distributions; for Λ(1520), we use one Breit-Wigner function. The obtained signal shapes are fixed in the later data fit. We use a 2nd-order polynomial function to model the background shape in the resonance mass spectrum. The different components of the fit function are the resonance signal (peaking in all spectra), genuine four-body signal (only peaking in  Δ E and M_ bc), background with resonances produced by other processes (only peaking in  M_ res) and non-peaking background. In contrast to fixed peaking shapes, all non-peaking shapes are floated and determined from the fit. Figure <ref> shows the fit results for  () and  (). Figure <ref> shows the fit result of . Figure <ref> shows the fit result of . After applying charmonia veto, the fit results of  and  are shown in Fig. <ref>.

In the mass window of η_c, we observe a clear resonance in M(pK^-), at the nominal mass of Λ(1520), indicating a non-negligible fraction of  from . In the same manner, we fit the Δ E, M_bc, M(pΛ̅K^-) and M(pK^-) spectra simultaneously in order to determine the yields of  and . The fit results are shown in Fig. <ref>.

The value of the signal significance is defined by √(-2×ln(ℒ_0/ℒ_s)) (σ), where ℒ_0 is the likelihood with null signal yield and  ℒ_s is the likelihood with measured yield. In the above calculation, we have used the likelihood function which is smeared by considering the additive systematic uncertainties that would affect the fitted yield. For those modes with signal significance less than 3σ, we integrate the smeared likelihood function in order to find out the upper limit yield at the 90% confidence level. That is, to calculate N that satisfies


    ∫_0^Nℒ(n)dn=0.9∫_0^∞ℒ(n)dn,

where ℒ(n) denotes the likelihood function with the condition that the number of signal events is fixed to the value n.

For systematic uncertainty, we consider tracking uncertainty per charged track (0.35% per track and 0.70% for Λ). The uncertainty of the estimated number of BB̅ pairs is 1.4%. The Λ selection uncertainty is determined by the difference of the flight-distance distribution between data and MC (3.0%). Some of systematic uncertainties are mode-dependent. The uncertainty in proton/antiproton identification is determined by using the study of Λ/Λ̅ (0.38% to 0.53%) in data, while the uncertainty in kaon identification is determined from the study of D^*+→ D^0π^+, D^0 → K^- π^+ in data (2.0% to 3.7%). We generate two kinds of signal MC: one considering a threshold enhancement in the dibaryonic system, the other with only phase space decays, and we mix the two samples to mimic the real data. The MC modeling uncertainty is set to be the larger difference in reconstruction efficiency between the threshold enhancement MC and phase space MC (0.52% to 9.3%). The smallest value, 0.52%, is for  due to limited phase space. The uncertainty from the fixed signal probability density function is obtained by varying all of the shape variables by one sigma and refitting (2.7% to 3.3%). The statistical uncertainty of the MC reconstruction efficiency is 0.31% to 0.47%. The uncertainty of qq̅ suppression is obtained from the reconstruction efficiency difference with and without the cut (0.50% to 5.0%). We apply the D^0 veto to redo the analysis and attribute the possible veto uncertainty 2.2% to 7.4%, where the statistical uncertainty from data is included. All the above uncertainties are combined in quadrature to obtain the total systematic uncertainties (5.9% to 12%).

Table <ref> summarizes the fit yields, reconstruction efficiencies and corresponding systematic uncertainties of significant and evident modes; Table <ref> summarizes the upper limit yields and reconstruction efficiencies for modes with signal significance less than 3σ. Note that the reconstruction efficiencies in Table <ref> and Table <ref> include the decay branching fraction 63.9% for the long-lived Λ→ pπ^- in the MC simulation and efficiencies have been corrected for the MC-data difference of the proton/kaon identification.

We use the world average values <cit.> of ℬ(Υ(4S) → B^+B^-), ℬ(ϕ→ K^+K^-), ℬ(Λ(1520) → pK^-), ℬ(), ℬ() and ℬ(), to obtain the results listed in Table <ref>. The measured branching fractions of four-body decay of  and  are consistent with theoretical predictions <cit.>. Note that ℬ(B^+ → p Λ̅ K^+ K^-) is compatible with ℬ(B^+ → p Λ̅π^+ π^-) <cit.>.
























In summary, using a sample of 772 × 10^6 BB̅ pair events, we measure the branching fractions of the four-body decays  and   with intermediate resonance modes being excluded. The feature of a threshold enhancement of the dibaryon system persists, but with a non-negligible phase space contribution. We also observe the three-body decay of +c.c. The measured ℬ(+c.c.) is in good agreement with the world average <cit.>. We also confirm the observation of +c.c. These decay amplitudes can be useful for a better understanding of the charmonium system. We observe the charmless decay  with a smaller branching fraction than that of the four-body decay. Its signal yield is not significant enough to perform an angular analysis.



We thank the KEKB group for excellent operation of the
accelerator; the KEK cryogenics group for efficient solenoid
operations; and the KEK computer group, the NII, and
PNNL/EMSL for valuable computing and SINET5 network support.
We acknowledge support from MEXT, JSPS and Nagoya's TLPRC (Japan);
ARC (Australia); FWF (Austria); NSFC and CCEPP (China);
MSMT (Czechia); CZF, DFG, EXC153, and VS (Germany);
DST (India); INFN (Italy);
MOE, MSIP, NRF, RSRI, FLRFAS project and GSDC of KISTI (Korea);
MNiSW and NCN (Poland); MES under contract 14.W03.31.0026 (Russia); ARRS (Slovenia);
IKERBASQUE and MINECO (Spain);
SNSF (Switzerland); MOE and MOST (Taiwan); and DOE and NSF (USA).






