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arXiv · 1910.10915

Observation of the radiative decays of $\Upsilon(1S)$ to $\chi_{c1}$

P. Katrenko·I. Adachi·H. Aihara·S. Al Said·D. M. Asner·T. Aushev·I. Badhrees·S. Bahinipati·P. Behera·C. Beleno·J. Bennett·V. Bhardwaj·B. Bhuyan·J. Biswal·A. Bobrov·G. Bonvicini·M. Bracko·M. Campajola·L. Cao·D. Cervenkov·V. Chekelian·A. Chen·B. G. Cheon·K. Chilikin·H. E. Cho·K. Cho·S. -K. Choi·Y. Choi·S. Choudhury·D. Cinabro·S. Cunliffe·F. Di Capua·S. Di Carlo·Z. Dolezal·T. V. Dong·S. Eidelman·D. Epifanov·J. E. Fast·B. G. Fulsom·R. Garg·V. Gaur·N. Gabyshev·A. Garmash·A. Giri·P. Goldenzweig·B. Golob·O. Grzymkowska·O. Hartbrich·K. Hayasaka·H. Hayashii·W. -S. Hou·T. Iijima·K. Inami·A. Ishikawa·R. Itoh·M. Iwasaki·Y. Iwasaki·W. W. Jacobs·H. B. Jeon·S. Jia·Y. Jin·D. Joffe·K. K. Joo·G. Karyan·H. Kichimi·D. Y. Kim·K. T. Kim·S. H. Kim·K. Kinoshita·P. Kodys·S. Korpar·R. Kroeger·T. Kuhr·I. S. Lee·S. C. Lee·P. Lewis·Y. B. Li·L. Li Gioi·J. Libby·K. Lieret·C. MacQueen·M. Masuda·T. Matsuda·D. Matvienko·M. Merola·K. Miyabayashi·H. Miyata·R. Mizuk·G. B. Mohanty·T. J. Moon·T. Mori·R. Mussa·E. Nakano·T. Nakano·M. Nakao·M. Nayak·N. K. Nisar·S. Nishida·K. Nishimura·H. Ono
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Abstract

We report the first observation of the radiative decay of the $\Upsilon(1S)$ into a charmonium state. The statistical significance of the observed signal of $\Upsilon(1S) \to \gamma \chi_{c1}$ is 6.3 standard deviations including systematics. The branching fraction is calculated to be Br($\Upsilon(1S) \to \gamma \chi_{c1}$) = (4.7^{+2.4}_{-1.8} (stat) ^{+0.4}_{-0.5} (sys)) * 10^{-5}. We also searched for $\Upsilon(1S)$ radiative decays into $\chi_{c0,2}$ and $\eta_c(1S,2S)$ and set upper limits on their branching fractions. These results are obtained from a 24.9 fb^{-1} data sample collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider at a center-of-mass energy equal to the $\Upsilon(2S)$ mass using $\Upsilon(1S)$ tagging by the $\Upsilon(2S) \to \Upsilon(1S) \pi^+\pi^-$ transitions.

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P. Katrenko, I. Adachi, H. Aihara, S. Al Said, D. M. Asner, T. Aushev, I. Badhrees, S. Bahinipati, P. Behera, C. Beleno, J. Bennett, V. Bhardwaj, B. Bhuyan, J. Biswal, A. Bobrov, G. Bonvicini, M. Bracko, M. Campajola, L. Cao, D. Cervenkov, V. Chekelian, A. Chen, B. G. Cheon, K. Chilikin, H. E. Cho, K. Cho, S. -K. Choi, Y. Choi, S. Choudhury, D. Cinabro, S. Cunliffe, F. Di Capua, S. Di Carlo, Z. Dolezal, T. V. Dong, S. Eidelman, D. Epifanov, J. E. Fast, B. G. Fulsom, R. Garg, V. Gaur, N. Gabyshev, A. Garmash, A. Giri, P. Goldenzweig, B. Golob, O. Grzymkowska, O. Hartbrich, K. Hayasaka, H. Hayashii, W. -S. Hou, T. Iijima, K. Inami, A. Ishikawa, R. Itoh, M. Iwasaki, Y. Iwasaki, W. W. Jacobs, H. B. Jeon, S. Jia, Y. Jin, D. Joffe, K. K. Joo, G. Karyan, H. Kichimi, D. Y. Kim, K. T. Kim, S. H. Kim, K. Kinoshita, P. Kodys, S. Korpar, R. Kroeger, T. Kuhr, I. S. Lee, S. C. Lee, P. Lewis, Y. B. Li, L. Li Gioi, J. Libby, K. Lieret, C. MacQueen, M. Masuda, T. Matsuda, D. Matvienko, M. Merola, K. Miyabayashi, H. Miyata, R. Mizuk, G. B. Mohanty, T. J. Moon, T. Mori, R. Mussa, E. Nakano, T. Nakano, M. Nakao, M. Nayak, N. K. Nisar, S. Nishida, K. Nishimura, H. Ono. 2019-10-24. Observation of the radiative decays of $\Upsilon(1S)$ to $\chi_{c1}$. https://doi.org/10.1103/physrevlett.124.122001

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