2014•Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fieldsOpen access
Study of B0→ρ0ρ0 decays, implications for the CKM angle ϕ2 and search for other B0 decay modes with a four-pion final state
P. Vanhoefer, Jeremy Peter Dalseno, C. Kiesling, Ichiro Adachi, H. Aihara, David M. Asner, V. Aulchenko, T. Aushev, A. M. Bakich, Abdullahi Ali Bala, Vishal Bhardwaj, B. Bhuyan, G. Bonvicini, Andrzej Bozek, M. Bračko, Thomas E. Browder, M.-C. Chang, P. Chang, Vladimir Chekelian, A. Chen, Pisin Chen, B. G. Cheon, K. Chilikin, R. Chistov, K. Cho, V. Chobanova, Y. Choi, D. Cinabro, Z. Doležal, Zbyněk Drásal, S. Eidelman, H. Farhat, J. E. Fast, T. Ferber, V. Gaur, N. Gabyshev, Sudeshna Ganguly, Alexey Garmash, Roland Gillard, Y. M. Goh, B. Golob, T. Hara, K. Hayasaka, Hisaki Hayashii, T. Higuchi, Y. Horii, Y. Hoshi, W.-S. Hou, H. J. Hyun, Toru Iijima, A. Ishikawa, R. Itoh, M. Iwasaki, T. Iwashita, I. Jaeglé, T. Julius, Dong Ha Kah, E. Kato, H. Kawai, T. Kawasaki, D. Y. Kim, H. O. Kim, J. B. Kim, J. H. Kim, M. J. Kim, Y. J. Kim, K. Kinoshita, J. Klucar, B. R. Ko, S. Korpar, P. Križan, P. Krokovny, B. Kronenbitter, T. Kuhr, Tetsuro Kumita, Alexander S. Kuzmin, Y.-J. Kwon, Jens Sören Lange, Soohyung Lee, Jingyan Li, L. Li Gioi, James Frederick Libby, C. Liu, Y. Liu, Dmitri Liventsev, P. Lukin, Kenkichi Miyabayashi, H. Miyata, R. Mizuk, G. B. Mohanty, A. Moll, H. G. Moser, R. Mussa, E. Nakano, Marcelo Nakao, Z. Natkaniec, E. Nedelkovska, N. K. Nisar, Shohei Nishida, Osamu Nitoh, S. Ogawa, Pavel N. Pakhlov, Galina V. Pakhlova, C. W. Park, H. Park, H. K. Park, T. K. Pedlar, R. Pestotnik, M. Petrič, L. E. Piilonen, Martin Ritter, M. Röhrken, Armine Rostomyan, Seunghwa Ryu, H. Sahoo, T. Saito, Y. Sakai, Saurabh Sandilya, Luka Santelj, T. Sanuki, Y. Sato, V. Savinov, O. Schneider, G. Schnell, Christoph Schwanda, A. J. Schwartz, D. Semmler, Katsumi Senyo, O. Seon, Martin E. Sevior, M. Shapkin, C. P. Shen, T.-A. Shibata, J.-G. Shiu, Boris Shwartz, A. Sibidanov, Frank Simon, Y.-S. Sohn, A. Sokolov, Elena Solovieva, Marko Starič, M. Steder, Takayuki Sumiyoshi, Umberto Tamponi, G. Tatishvili, Y. Teramoto, Karim Trabelsi, Toru Tsuboyama, Makoto Uchida, S. Uehara, Y. Unno, S. Uno, Sven E. Vahsen, C. Van Hulse, Gary S. Varner, K. E. Varvell, A. Vinokurova, V. Vorobyev, M. N. Wagner, C. H. Wang, M.-Z. Wang, P. Wang, X. L. Wang, Y. Watanabe, K. M. Williams, Eunil Won, Y. Yamashita, S. Yashchenko, Y. Yook, Z. P. Zhang, V. N. Zhilich, Vladimir V. Zhulanov, Anže Zupanc
Abstract
We present a study of the branching fraction of the decay ${B}^{0}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{0}{\ensuremath{\rho}}^{0}$ and the fraction of longitudinally polarized ${\ensuremath{\rho}}^{0}$ mesons in this decay. The results are obtained from the final data sample containing $772\ifmmode\times\else\texttimes\fi{}1{0}^{6}$ $B\overline{B}$ pairs collected at the $\mathrm{\ensuremath{\Upsilon}}(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy ${e}^{+}{e}^{\ensuremath{-}}$ collider. We find $166\ifmmode\pm\else\textpm\fi{}59$ ${B}^{0}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{0}{\ensuremath{\rho}}^{0}$ events (including systematic uncertainties), corresponding to a branching fraction of $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{0}{\ensuremath{\rho}}^{0})=(1.02\ifmmode\pm\else\textpm\fi{}0.30(\text{stat})\ifmmode\pm\else\textpm\fi{}0.15(\text{syst}))\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}6}$ with a significance of 3.4 standard deviations and a longitudinal polarization fraction ${f}_{L}=0.2{1}_{\ensuremath{-}0.22}^{+0.18}(\text{stat})\ifmmode\pm\else\textpm\fi{}0.15(\text{syst})$. We use the longitudinal polarization fraction to determine the Cabibbo-Kobayashi-Maskawa matrix angle ${\ensuremath{\phi}}_{2}=(84.9\ifmmode\pm\else\textpm\fi{}13.5)\ifmmode^\circ\else\textdegree\fi{}$ through an isospin analysis in the $B\ensuremath{\rightarrow}\ensuremath{\rho}\ensuremath{\rho}$ system. We furthermore find $125\ifmmode\pm\else\textpm\fi{}41$ ${B}^{0}\ensuremath{\rightarrow}{f}_{0}{\ensuremath{\rho}}^{0}$ events, corresponding to $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{f}_{0}{\ensuremath{\rho}}^{0})\ifmmode\times\else\texttimes\fi{}\mathcal{B}({f}_{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})=(0.78\ifmmode\pm\else\textpm\fi{}0.22(\text{stat})\ifmmode\pm\else\textpm\fi{}\phantom{\rule{0ex}{0ex}}0.11(\text{syst}))\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}6}$, 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, $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})<11.2\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}6}$, $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{0}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})<12.0\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}6}$, $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{f}_{0}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})\ifmmode\times\else\texttimes\fi{}\mathcal{B}({f}_{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})<3.0\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}6}$ and $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{f}_{0}{f}_{0})\ifmmode\times\else\texttimes\fi{}\mathcal{B}({f}_{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{)}^{2}<0.2\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}6}$.