Measurement of eta_c(1S), eta_c(2S) and non-resonant eta' pi+ pi- production via two-photon collisions

The Belle Collaboration: Q. N. Xu , I. Adachi , H. Aihara , S. Al Said , D. M. Asner , H. Atmacan , V. Aulchenko , T. Aushev

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R. Ayad V. Babu I. Badhrees A. M. Bakich V. Bansal E. Barberio P. Behera M. Berger V. Bhardwaj B. Bhuyan J. Biswal A. Bondar A. Bozek M. Bra\v{c}ko D. \v{C}ervenkov A. Chen B. G. Cheon K. Chilikin K. Cho S.-K. Choi Y. Choi D. Cinabro S. Cunliffe T. Czank N. Dash S. Di Carlo Z. Dole\v{z}al Z. Dr\'asal S. Eidelman D. Epifanov J. E. Fast T. Ferber B. G. Fulsom R. Garg V. Gaur N. Gabyshev A. Garmash M. Gelb P. Goldenzweig Y. Guan E. Guido J. Haba K. Hayasaka H. Hayashii M. T. Hedges W.-S. Hou K. Inami G. Inguglia A. Ishikawa R. Itoh M. Iwasaki Y. Iwasaki I. Jaegle H. B. Jeon Y. Jin K. K. Joo T. Julius A. B. Kaliyar K. H. Kang G. Karyan T. Kawasaki H. Kichimi C. Kiesling D. Y. Kim H. J. Kim J. B. Kim P. Kody\v{s} S. Korpar D. Kotchetkov P. Kri\v{z}an R. Kroeger P. Krokovny R. Kulasiri Y.-J. Kwon I. S. Lee S. C. Lee L. K. Li Y. Li L. Li Gioi J. Libby D. Liventsev M. Lubej T. Luo M. Masuda T. Matsuda D. Matvienko M. Merola K. Miyabayashi H. Miyata R. Mizuk H. K. Moon T. Mori R. Mussa T. Nanut K. J. Nath Z. Natkaniec M. Nayak N. K. Nisar S. Nishida S. Okuno H. Ono Y. Onuki P. Pakhlov G. Pakhlova B. Pal H. Park S. Paul T. K. Pedlar R. Pestotnik L. E. Piilonen V. Popov M. Ritter A. Rostomyan G. Russo Y. Sakai M. Salehi S. Sandilya T. Sanuki V. Savinov O. Schneider G. Schnell C. Schwanda Y. Seino K. Senyo O. Seon M. E. Sevior V. Shebalin C. P. Shen T.-A. Shibata N. Shimizu J.-G. Shiu A. Sokolov E. Solovieva M. Stari\v{c} J. F. Strube T. Sumiyoshi M. Takizawa U. Tamponi K. Tanida F. Tenchini M. Uchida S. Uehara T. Uglov Y. Unno S. Uno P. Urquijo C. Van Hulse G. Varner A. Vinokurova V. Vorobyev A. Vossen B. Wang C. H. Wang M.-Z. Wang P. Wang X. L. Wang M. Watanabe Y. Watanabe E. Widmann E. Won H. Ye C. Z. Yuan Y. Yusa S. Zakharov C. C. Zhang Z. P. Zhang V. Zhilich V. Zhukova V. Zhulanov A. Zupanc

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keywords gammastatsystmassmeasuredwidthdecaydecays

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We report the measurement of gamma gamma to eta_c(1S), eta_c(2S) to eta' pi+ pi- with eta' decays to gamma rho and eta pi+ pi- using 941 fb^{-1} of data collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. The eta_c(1S) mass and width are measured to be M = [2984.6\pm0.7 (stat.)\pm2.2 (syst.)] MeV/c^{2} and \Gamma = [30.8^{+2.3}_{-2.2}~(stat.) \pm 2.5~(syst.)] MeV, respectively. First observation of eta_c(2S) to eta' pi+ pi- with a significance of 5.5sigma including systematic error is obtained, and the eta_c(2S) mass is measured to be M = [3635.1\pm3.7~(stat.)\pm2.9~(syst.)] MeV/c^{2}. The products of the two-photon decay width and branching fraction (B) of decays to eta'pi+ pi- are determined to be \Gamma_{gamma gamma}B = [65.4\pm2.6~(stat.)\pm6.9~(syst.)] eV for eta_c(1S) and [5.6^{+1.2}_{-1.1}~(stat.)\pm1.1~(syst.)] eV for eta_c(2S). A new decay mode for the eta_c(1S) to eta'f_0(2080) with f_0(2080) to pi+ pi- is observed with a statistical significance of 20sigma. The f_0(2080) mass and width are determined to be M = [2083^{+63}_{-66}~(stat.)\pm 32~(syst.)] MeV/c^{2} and \Gamma = [178^{+60}_{-178}~(stat.) \pm 55~(syst.)] MeV. The cross sections for gamma gamma to eta' pi+ pi- and eta'f_{2}(1270) are measured for the first time.

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Measurement of eta_c(1S), eta_c(2S) and non-resonant eta' pi+ pi- production via two-photon collisions

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