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Study of $B^{0} \to ρ^{0} ρ^{0}$ decays, implications for the CKM angle $ϕ_{2}$ and search for other $B^{0}$ decay modes with a four-pion final state

P. Vanhoefer³², J. Dalseno^32,54, C. Kiesling³², I. Adachi¹², H. Aihara⁵⁸, D. M. Asner⁴⁵, V. Aulchenko³, T. Aushev²⁰, A. M. Bakich⁵² et al.

A. Bala⁴⁶, V. Bhardwaj³⁷, B. Bhuyan¹⁴, G. Bonvicini⁶³, A. Bozek⁴¹, M. Bračko^31,21, T. E. Browder¹¹, M.-C. Chang⁸, P. Chang⁴⁰, V. Chekelian³², A. Chen³⁸, P. Chen⁴⁰, B. G. Cheon¹⁰, K. Chilikin²⁰, R. Chistov²⁰, K. Cho²⁵, V. Chobanova³², Y. Choi⁵¹, D. Cinabro⁶³, Z. Doležal⁴, Z. Drásal⁴, S. Eidelman³, H. Farhat⁶³, J. E. Fast⁴⁵, T. Ferber⁷, V. Gaur⁵³, N. Gabyshev³, S. Ganguly⁶³, A. Garmash³, R. Gillard⁶³, Y. M. Goh¹⁰, B. Golob^29,21, T. Hara¹², K. Hayasaka³⁶, H. Hayashii³⁷, T. Higuchi²⁴, Y. Horii³⁶, Y. Hoshi⁵⁶, W.-S. Hou⁴⁰, H. J. Hyun²⁷, T. Iijima^36,35, A. Ishikawa⁵⁷, R. Itoh¹², Y. Iwasaki¹², T. Iwashita³⁷, I. Jaegle¹¹, T. Julius³³, D. H. Kah²⁷, E. Kato⁵⁷, H. Kawai⁵, T. Kawasaki⁴³, D. Y. Kim⁵⁰, H. O. Kim²⁷, J. B. Kim²⁶, J. H. Kim²⁵, M. J. Kim²⁷, Y. J. Kim²⁵, K. Kinoshita⁶, J. Klucar²¹, B. R. Ko²⁶, S. Korpar^31,21, P. Križan^29,21, P. Krokovny³, B. Kronenbitter²³, T. Kuhr²³, T. Kumita⁶⁰, A. Kuzmin³, Y.-J. Kwon⁶⁵, J. S. Lange⁹, S.-H. Lee²⁶, J. Li⁴⁹, L. Li Gioi³², J. Libby¹⁵, C. Liu⁴⁸, Y. Liu⁶, D. Liventsev¹², P. Lukin³, K. Miyabayashi³⁷, H. Miyata⁴³, R. Mizuk^20,34, G. B. Mohanty⁵³, A. Moll^32,54, H.-G. Moser³², R. Mussa¹⁹, E. Nakano⁴⁴, M. Nakao¹², Z. Natkaniec⁴¹, E. Nedelkovska³², N. K. Nisar⁵³, S. Nishida¹², O. Nitoh⁶¹, S. Ogawa⁵⁵, P. Pakhlov^20,34, G. Pakhlova²⁰, C. W. Park⁵¹, H. Park²⁷, H. K. Park²⁷, T. K. Pedlar³⁰, R. Pestotnik²¹, M. Petrič²¹, L. E. Piilonen⁶², M. Ritter³², M. Röhrken²³, A. Rostomyan⁷, S. Ryu⁴⁹, H. Sahoo¹¹, T. Saito⁵⁷, Y. Sakai¹², S. Sandilya⁵³, L. Santelj²¹, T. Sanuki⁵⁷, Y. Sato⁵⁷, V. Savinov⁴⁷, O. Schneider²⁸, G. Schnell^1,13, C. Schwanda¹⁷, A. J. Schwartz⁶, D. Semmler⁹, K. Senyo⁶⁴, O. Seon³⁵, M. E. Sevior³³, M. Shapkin¹⁸, C. P. Shen², T.-A. Shibata⁵⁹, J.-G. Shiu⁴⁰, B. Shwartz³, A. Sibidanov⁵², F. Simon^32,54, Y.-S. Sohn⁶⁵, A. Sokolov¹⁸, E. Solovieva²⁰, M. Starič²¹, M. Steder⁷, T. Sumiyoshi⁶⁰, U. Tamponi^19,66, G. Tatishvili⁴⁵, Y. Teramoto⁴⁴, K. Trabelsi¹², T. Tsuboyama¹², M. Uchida⁵⁹, S. Uehara¹², Y. Unno¹⁰, S. Uno¹², S. E. Vahsen¹¹, C. Van Hulse¹, G. Varner¹¹, K. E. Varvell⁵², A. Vinokurova³, V. Vorobyev³, M. N. Wagner⁹, C. H. Wang³⁹, M.-Z. Wang⁴⁰, P. Wang¹⁶, X. L. Wang⁶², Y. Watanabe²², K. M. Williams⁶², E. Won²⁶, Y. Yamashita⁴², S. Yashchenko⁷, Y. Yook⁶⁵, Z. P. Zhang⁴⁸, V. Zhilich³, V. Zhulanov³, and A. Zupanc²³

¹University of the Basque Country UPV/EHU, 48080 Bilbao
²Beihang University, Beijing 100191
³Budker Institute of Nuclear Physics SB RAS and Novosibirsk State University, Novosibirsk 630090
⁴Faculty of Mathematics and Physics, Charles University, 121 16 Prague
⁵Chiba University, Chiba 263-8522
⁶University of Cincinnati, Cincinnati, Ohio 45221
⁷Deutsches Elektronen–Synchrotron, 22607 Hamburg
⁸Department of Physics, Fu Jen Catholic University, Taipei 24205
⁹Justus-Liebig-Universität Gießen, 35392 Gießen
¹⁰Hanyang University, Seoul 133-791
¹¹University of Hawaii, Honolulu, Hawaii 96822
¹²High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801
¹³Ikerbasque, 48011 Bilbao
¹⁴Indian Institute of Technology Guwahati, Assam 781039
¹⁵Indian Institute of Technology Madras, Chennai 600036
¹⁶Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049
¹⁷Institute of High Energy Physics, Vienna 1050
¹⁸Institute for High Energy Physics, Protvino 142281
¹⁹INFN - Sezione di Torino, 10125 Torino
²⁰Institute for Theoretical and Experimental Physics, Moscow 117218
²¹J. Stefan Institute, 1000 Ljubljana
²²Kanagawa University, Yokohama 221-8686
²³Institut für Experimentelle Kernphysik, Karlsruher Institut für Technologie, 76131 Karlsruhe
²⁴Kavli Institute for the Physics and Mathematics of the Universe (WPI), University of Tokyo, Kashiwa 277-8583
²⁵Korea Institute of Science and Technology Information, Daejeon 305-806
²⁶Korea University, Seoul 136-713
²⁷Kyungpook National University, Daegu 702-701
²⁸École Polytechnique Fédérale de Lausanne (EPFL), Lausanne 1015
²⁹Faculty of Mathematics and Physics, University of Ljubljana, 1000 Ljubljana
³⁰Luther College, Decorah, Iowa 52101
³¹University of Maribor, 2000 Maribor
³²Max-Planck-Institut für Physik, 80805 München
³³School of Physics, University of Melbourne, Victoria 3010
³⁴Moscow Physical Engineering Institute, Moscow 115409
³⁵Graduate School of Science, Nagoya University, Nagoya 464-8602
³⁶Kobayashi-Maskawa Institute, Nagoya University, Nagoya 464-8602
³⁷Nara Women’s University, Nara 630-8506
³⁸National Central University, Chung-li 32054
³⁹National United University, Miao Li 36003
⁴⁰Department of Physics, National Taiwan University, Taipei 10617
⁴¹H. Niewodniczanski Institute of Nuclear Physics, Krakow 31-342
⁴²Nippon Dental University, Niigata 951-8580
⁴³Niigata University, Niigata 950-2181
⁴⁴Osaka City University, Osaka 558-8585
⁴⁵Pacific Northwest National Laboratory, Richland, Washington 99352
⁴⁶Panjab University, Chandigarh 160014
⁴⁷University of Pittsburgh, Pittsburgh, Pennsylvania 15260
⁴⁸University of Science and Technology of China, Hefei 230026
⁴⁹Seoul National University, Seoul 151-742
⁵⁰Soongsil University, Seoul 156-743
⁵¹Sungkyunkwan University, Suwon 440-746
⁵²School of Physics, University of Sydney, New South Wales 2006
⁵³Tata Institute of Fundamental Research, Mumbai 400005
⁵⁴Excellence Cluster Universe, Technische Universität München, 85748 Garching
⁵⁵Toho University, Funabashi 274-8510
⁵⁶Tohoku Gakuin University, Tagajo 985-8537
⁵⁷Tohoku University, Sendai 980-8578
⁵⁸Department of Physics, University of Tokyo, Tokyo 113-0033
⁵⁹Tokyo Institute of Technology, Tokyo 152-8550
⁶⁰Tokyo Metropolitan University, Tokyo 192-0397
⁶¹Tokyo University of Agriculture and Technology, Tokyo 184-8588
⁶²CNP, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061
⁶³Wayne State University, Detroit, Michigan 48202
⁶⁴Yamagata University, Yamagata 990-8560
⁶⁵Yonsei University, Seoul 120-749
⁶⁶University of Torino, 10124 Torino

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Phys. Rev. D 89, 072008 – Published 8 April, 2014Erratum Phys. Rev. D 89, 119903 (2014)

DOI: https://doi.org/10.1103/PhysRevD.89.072008

Abstract

We present a study of the branching fraction of the decay $B^{0} \to ρ^{0} ρ^{0}$ and the fraction of longitudinally polarized $ρ^{0}$ mesons in this decay. The results are obtained from the final data sample containing $772 \times 1 0^{6}$ $B \bar{B}$ pairs collected at the $ϒ (4 S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+} e^{-}$ collider. We find $166 \pm 59$ $B^{0} \to ρ^{0} ρ^{0}$ events (including systematic uncertainties), corresponding to a branching fraction of $B (B^{0} \to ρ^{0} ρ^{0}) = (1.02 \pm 0.30 (stat) \pm 0.15 (syst)) \times 1 0^{- 6}$ with a significance of 3.4 standard deviations and a longitudinal polarization fraction $f_{L} = 0.2 1_{- 0.22}^{+ 0.18} (stat) \pm 0.15 (syst)$ . We use the longitudinal polarization fraction to determine the Cabibbo-Kobayashi-Maskawa matrix angle $ϕ_{2} = (84.9 \pm 13.5) °$ through an isospin analysis in the $B \to ρ ρ$ system. We furthermore find $125 \pm 41$ $B^{0} \to f_{0} ρ^{0}$ events, corresponding to $B (B^{0} \to f_{0} ρ^{0}) \times B (f_{0} \to π^{+} π^{-}) = (0.78 \pm 0.22 (stat) \pm 0.11 (syst)) \times 1 0^{- 6}$ , with a significance of 3.1 standard deviations. We find no other significant contribution with the same final state, and set upper limits at 90% confidence level on the (product) branching fractions, $B (B^{0} \to π^{+} π^{-} π^{+} π^{-}) < 11.2 \times 1 0^{- 6}$ , $B (B^{0} \to ρ^{0} π^{+} π^{-}) < 12.0 \times 1 0^{- 6}$ , $B (B^{0} \to f_{0} π^{+} π^{-}) \times B (f_{0} \to π^{+} π^{-}) < 3.0 \times 1 0^{- 6}$ and $B (B^{0} \to f_{0} f_{0}) \times B (f_{0} \to π^{+} π^{-})^{2} < 0.2 \times 1 0^{- 6}$ .