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arXiv · 1506.08914

First observation of the hadronic transition $ \Upsilon(4S) \to \eta h_{b}(1P)$ and new measurement of the $h_b(1P)$ and $\eta_b(1S)$ parameters

The Belle Collaboration·U. Tamponi·R. Mussa·A. Abdesselam·H. Aihara·K. Arinstein·D. M. Asner·H. Atmacan·T. Aushev·R. Ayad·I. Badhrees·A. M. Bakich·E. Barberio·V. Bhardwaj·B. Bhuyan·J. Biswal·A. Bondar·G. Bonvicini·A. Bozek·M. Bračko·T. E. Browder·D. Červenkov·A. Chen·B. G. Cheon·K. Cho·V. Chobanova·S. -K. Choi·Y. Choi·D. Cinabro·M. Danilov·Z. Doležal·Z. Drásal·A. Drutskoy·S. Eidelman·D. Epifanov·H. Farhat·J. E. Fast·T. Ferber·B. G. Fulsom·V. Gaur·N. Gabyshev·A. Garmash·D. Getzkow·R. Gillard·Y. M. Goh·B. Golob·J. Haba·K. Hayasaka·H. Hayashii·X. H. He·M. T. Hedges·W. -S. Hou·T. Iijima·K. Inami·A. Ishikawa·I. Jaegle·D. Joffe·T. Julius·E. Kato·P. Katrenko·H. Kichimi·C. Kiesling·D. Y. Kim·H. J. Kim·J. H. Kim·K. T. Kim·S. H. Kim·K. Kinoshita·P. Kodyš·S. Korpar·P. Križan·P. Krokovny·T. Kumita·A. Kuzmin·J. S. Lange·P. Lewis·J. Libby·P. Lukin·D. Matvienko·K. Miyabayashi·H. Miyata·R. Mizuk·G. B. Mohanty·A. Moll·T. Mori·E. Nakano·M. Nakao·T. Nanut·Z. Natkaniec·M. Nayak·N. K. Nisar·S. Nishida·S. Ogawa·S. Okuno·S. L. Olsen·W. Ostrowicz·C. Oswald·G. Pakhlova·B. Pal·H. Park
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Abstract

Using a sample of $771.6 \times 10^{6}$ $\Upsilon(4S)$ decays collected by the Belle experiment at the KEKB $e^+e^-$ collider, we observe for the first time the transition $\Upsilon(4S) \to \eta h_b(1P)$ with the branching fraction ${\cal B}[\Upsilon(4S) \to \eta h_b(1P)]= (2.18 \pm 0.11 \pm 0.18) \times 10^{-3}$ and we measure the $h_b(1P)$ mass $M_{h_{b}(1P)} = (9899.3 \pm 0.4 \pm 1.0)$ MeV/$c^{2}$, corresponding to the hyperfine splitting $\Delta M_{\mathrm HF}(1P) = (0.6 \pm 0.4 \pm 1.0)$ MeV/$c^{2}$. Using the transition $h_b(1P) \to \gamma \eta_b(1S)$, we measure the $\eta_b(1S)$ mass $M_{\eta_{b}(1S)} = (9400.7 \pm 1.7 \pm 1.6)$ MeV/$c^{2}$, corresponding to $\Delta M_{\mathrm HF}(1S) = (59.6 \pm 1.7 \pm 1.6)$ MeV/$c^{2}$, the $\eta_b(1S)$ width $\Gamma_{\eta_{b}(1S)} = (8 ^{+6}_{-5} \pm 5)$ MeV/$c^{2}$ and the branching fraction ${\cal B}[h_b(1P) \to \gamma \eta_b(1S)]= (56 \pm 8 \pm 4) \%$.

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The Belle Collaboration, U. Tamponi, R. Mussa, A. Abdesselam, H. Aihara, K. Arinstein, D. M. Asner, H. Atmacan, T. Aushev, R. Ayad, I. Badhrees, A. M. Bakich, E. Barberio, V. Bhardwaj, B. Bhuyan, J. Biswal, A. Bondar, G. Bonvicini, A. Bozek, M. Bračko, T. E. Browder, D. Červenkov, A. Chen, B. G. Cheon, K. Cho, V. Chobanova, S. -K. Choi, Y. Choi, D. Cinabro, M. Danilov, Z. Doležal, Z. Drásal, A. Drutskoy, S. Eidelman, D. Epifanov, H. Farhat, J. E. Fast, T. Ferber, B. G. Fulsom, V. Gaur, N. Gabyshev, A. Garmash, D. Getzkow, R. Gillard, Y. M. Goh, B. Golob, J. Haba, K. Hayasaka, H. Hayashii, X. H. He, M. T. Hedges, W. -S. Hou, T. Iijima, K. Inami, A. Ishikawa, I. Jaegle, D. Joffe, T. Julius, E. Kato, P. Katrenko, H. Kichimi, C. Kiesling, D. Y. Kim, H. J. Kim, J. H. Kim, K. T. Kim, S. H. Kim, K. Kinoshita, P. Kodyš, S. Korpar, P. Križan, P. Krokovny, T. Kumita, A. Kuzmin, J. S. Lange, P. Lewis, J. Libby, P. Lukin, D. Matvienko, K. Miyabayashi, H. Miyata, R. Mizuk, G. B. Mohanty, A. Moll, T. Mori, E. Nakano, M. Nakao, T. Nanut, Z. Natkaniec, M. Nayak, N. K. Nisar, S. Nishida, S. Ogawa, S. Okuno, S. L. Olsen, W. Ostrowicz, C. Oswald, G. Pakhlova, B. Pal, H. Park. 2015-06-30. First observation of the hadronic transition $ \Upsilon(4S) \to \eta h_{b}(1P)$ and new measurement of the $h_b(1P)$ and $\eta_b(1S)$ parameters. https://doi.org/10.1103/physrevlett.115.142001

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