Observation of the radiative decays of $\Upsilon(1S)$ to $\chi_{c1}$
- Katrenko, P.
- Adachi, I.
- Bennett, J.
- Onuki, Y.
- Oskin, P.
- Pakhlov, P.
- Pakhlova, G.
- Pang, T.
- Pardi, S.
- Park, C. W.
- Park, H.
- Park, S. -H.
- Paul, S.
- Bhardwaj, V.
- Pedlar, T. K.
- Pestotnik, R.
- Piilonen, L. E.
- Popov, V.
- Prencipe, E.
- Prim, M. T.
- Ritter, M.
- Rostomyan, A.
- Rout, N.
- Russo, G.
- Bhuyan, B.
- Sahoo, D.
- Sakai, Y.
- Sandilya, S.
- Sanuki, T.
- Savinov, V.
- Schneider, O.
- Schnell, G.
- Schueler, J.
- Schwanda, C.
- Seino, Y.
- Biswal, J.
- Senyo, K.
- Sevior, M. E.
- Shen, C. P.
- Shiu, J. -G.
- Solovieva, E.
- Staric, M.
- Stottler, Z. S.
- Sumiyoshi, T.
- Sutcliffe, W.
- Takizawa, M.
- Bobrov, A.
- Tamponi, U.
- Tanida, K.
- Tenchini, F.
- Trabelsi, K.
- Uchida, M.
- Uehara, S.
- Uglov, T.
- Unno, Y.
- Uno, S.
- Urquijo, P.
- Bonvicini, G.
- Usov, Y.
- Van Tonder, R.
- Varner, G.
- Vossen, A.
- Wang, B.
- Wang, C. H.
- Wang, M. -Z.
- Wang, P.
- Wang, X. L.
- Won, E.
- Bracko, M.
- Yang, S. B.
- Ye, Hua
- Yelton, J.
- Yin, J. H.
- Yuan, C. Z.
- Yusa, Y.
- Zhang, Z. P.
- Zhilich, V.
- Zhukova, V.
- Belle Collaboration
- Campajola, M.
- Cao, L.
- Cervenkov, D.
- Aihara, H.
- Chekelian, V.
- Chen, A.
- Cheon, B. G.
- Chilikin, K.
- Cho, H. E.
- Cho, K.
- Choi, S. -K.
- Choi, Y.
- Choudhury, S.
- Cinabro, D.
- Said, S. Al
- Cunliffe, S.
- Di Capua, F.
- Di Carlo, S.
- Dolezal, Z.
- Dong, T. V.
- Eidelman, S.
- Epifanov, D.
- Fast, J. E.
- Fulsom, B. G.
- Garg, R.
- Asner, D. M.
- Gaur, V.
- Gabyshev, N.
- Garmash, A.
- Giri, A.
- Goldenzweig, P.
- Golob, B.
- Grzymkowska, O.
- Hartbrich, O.
- Hayasaka, K.
- Hayashii, H.
- Aushev, T.
- Hou, W. -S.
- Iijima, T.
- Inami, K.
- Ishikawa, A.
- Itoh, R.
- Iwasaki, M.
- Iwasaki, Y.
- Jacobs, W. W.
- Jeon, H. B.
- Jia, S.
- Badhrees, I.
- Jin, Y.
- Joffe, D.
- Joo, K. K.
- Karyan, G.
- Kichimi, H.
- Kim, D. Y.
- Kim, K. T.
- Kim, S. H.
- Kinoshita, K.
- Kodys, P.
- Bahinipati, S.
- Korpar, S.
- Kroeger, R.
- Kuhr, T.
- Lee, I. S.
- Lee, S. C.
- Lewis, P.
- Li, Y. B.
- Gioi, L. Li
- Libby, J.
- Lieret, K.
- Behera, P.
- MacQueen, C.
- Masuda, M.
- Matsuda, T.
- Matvienko, D.
- Merola, M.
- Miyabayashi, K.
- Miyata, H.
- Mizuk, R.
- Mohanty, G. B.
- Moon, T. J.
- Beleno, C.
- Mori, T.
- Mussa, R.
- Nakano, E.
- Nakano, T.
- Nakao, M.
- Nayak, M.
- Nisar, N. K.
- Nishida, S.
- Nishimura, K.
- Ono, H.
DOIAbstract
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)...