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

A. Bobrov; A. Chen; A. Garmash; A. Giri; A. Ishikawa; A. Rostomyan; A. Vossen; B. Bhuyan; B. G. Cheon; B. G. Fulsom

arxiv: 1910.10915 · v1 · pith:IC3VUKPRnew · submitted 2019-10-24 · ✦ hep-ex

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

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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 Y. Onuki P. Oskin P. Pakhlov G. Pakhlova T. Pang S. Pardi C. W. Park H. Park S.-H. Park S. Paul T. K. Pedlar R. Pestotnik L. E. Piilonen V. Popov E. Prencipe M. T. Prim M. Ritter A. Rostomyan N. Rout G. Russo D. Sahoo Y. Sakai S. Sandilya T. Sanuki V. Savinov O. Schneider G. Schnell J. Schueler C. Schwanda Y. Seino K. Senyo M. E. Sevior C. P. Shen J.-G. Shiu E. Solovieva M. Staric Z. S. Stottler T. Sumiyoshi W. Sutcliffe M. Takizawa U. Tamponi K. Tanida F. Tenchini K. Trabelsi M. Uchida S. Uehara T. Uglov Y. Unno S. Uno P. Urquijo Y. Usov R. Van Tonder G. Varner A. Vossen B. Wang C. H. Wang M.-Z. Wang P. Wang X. L. Wang E. Won S. B. Yang H. Ye J. Yelton J. H. Yin C. Z. Yuan Y. Yusa Z. P. Zhang V. Zhilich V. Zhukova

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keywords upsilonradiativebranchingdecaysgammaobservationasymmetric-energybelle

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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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Observation of the radiative decays of Upsilon(1S) to chi_(c1)

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