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Study of $ψ (2 S)$ decays to $γ p \bar{p}$ , $π^{0} p \bar{p}$ , and $η p \bar{p}$ , and search for $p \bar{p}$ threshold enhancements

J. P. Alexander¹, D. G. Cassel¹, S. Das¹, R. Ehrlich¹, L. Fields¹, L. Gibbons¹, S. W. Gray¹, D. L. Hartill¹, B. K. Heltsley¹ et al. (CLEO Collaboration)

B. K. Heltsley¹, D. L. Kreinick¹, V. E. Kuznetsov¹, J. R. Patterson¹, D. Peterson¹, D. Riley¹, A. Ryd¹, A. J. Sadoff¹, X. Shi¹, W. M. Sun¹, J. Yelton², P. Rubin³, N. Lowrey⁴, S. Mehrabyan⁴, M. Selen⁴, J. Wiss⁴, J. Libby⁵, M. Kornicer⁶, R. E. Mitchell⁶, M. R. Shepherd⁶, C. M. Tarbert⁶, D. Besson⁷, T. K. Pedlar⁸, J. Xavier⁸, D. Cronin-Hennessy⁹, J. Hietala⁹, P. Zweber⁹, S. Dobbs¹⁰, Z. Metreveli¹⁰, K. K. Seth¹⁰, A. Tomaradze¹⁰, T. Xiao¹⁰, S. Brisbane¹¹, L. Martin¹¹, A. Powell¹¹, P. Spradlin¹¹, G. Wilkinson¹¹, H. Mendez¹², J. Y. Ge¹³, D. H. Miller¹³, I. P. J. Shipsey¹³, B. Xin¹³, G. S. Adams¹⁴, D. Hu¹⁴, B. Moziak¹⁴, J. Napolitano¹⁴, K. M. Ecklund¹⁵, J. Insler¹⁶, H. Muramatsu¹⁶, C. S. Park¹⁶, L. J. Pearson¹⁶, E. H. Thorndike¹⁶, F. Yang¹⁶, S. Ricciardi¹⁷, C. Thomas^11,17, M. Artuso¹⁸, S. Blusk¹⁸, R. Mountain¹⁸, T. Skwarnicki¹⁸, S. Stone¹⁸, J. C. Wang¹⁸, L. M. Zhang¹⁸, G. Bonvicini¹⁹, D. Cinabro¹⁹, A. Lincoln¹⁹, M. J. Smith¹⁹, P. Zhou¹⁹, J. Zhu¹⁹, P. Naik²⁰, J. Rademacker²⁰, D. M. Asner^21,*, K. W. Edwards²¹, K. Randrianarivony²¹, G. Tatishvili^21,*, R. A. Briere²², H. Vogel²², P. U. E. Onyisi²³, and J. L. Rosner²³ (CLEO Collaboration)

¹Cornell University, Ithaca, New York 14853, USA
²University of Florida, Gainesville, Florida 32611, USA
³George Mason University, Fairfax, Virginia 22030, USA
⁴University of Illinois, Urbana-Champaign, Illinois 61801, USA
⁵Indian Institute of Technology Madras, Chennai, Tamil Nadu 600036, India
⁶Indiana University, Bloomington, Indiana 47405, USA
⁷University of Kansas, Lawrence, Kansas 66045, USA
⁸Luther College, Decorah, Iowa 52101, USA
⁹University of Minnesota, Minneapolis, Minnesota 55455, USA
¹⁰Northwestern University, Evanston, Illinois 60208, USA
¹¹University of Oxford, Oxford OX1 3RH, United Kingdom
¹²University of Puerto Rico, Mayaguez, Puerto Rico 00681
¹³Purdue University, West Lafayette, Indiana 47907, USA
¹⁴Rensselaer Polytechnic Institute, Troy, New York 12180, USA
¹⁵Rice University, Houston, Texas 77005, USA
¹⁶University of Rochester, Rochester, New York 14627, USA
¹⁷STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, United Kingdom
¹⁸Syracuse University, Syracuse, New York 13244, USA
¹⁹Wayne State University, Detroit, Michigan 48202, USA
²⁰University of Bristol, Bristol BS8 1TL, United Kingdom
²¹Carleton University, Ottawa, Ontario, Canada K1S 5B6
²²Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
²³University of Chicago, Chicago, Illinois 60637, USA

^*Present address: Pacific Northwest National Laboratory, Richland, WA 99352, USA.

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Phys. Rev. D 82, 092002 – Published 5 November, 2010

DOI: https://doi.org/10.1103/PhysRevD.82.092002

Abstract

The decays of $ψ (2 S)$ into $γ p \bar{p}$ , $π^{0} p \bar{p}$ , and $η p \bar{p}$ have been studied with the CLEO-c detector using a sample of $24.5 \times 10^{6}$ $ψ (2 S)$ events obtained from $e^{+} e^{-}$ annihilations at $\sqrt{s} = 3686 MeV$ . The data show evidence for the excitation of several $N^{*}$ resonances in $p π^{0}$ and $p η$ channels in $π^{0} p \bar{p}$ and $η p \bar{p}$ decays, and $f_{2}$ states in $γ p \bar{p}$ decay. Branching fractions for decays of $ψ (2 S)$ to $γ p \bar{p}$ , $π^{0} p \bar{p}$ , and $η p \bar{p}$ have been determined. No evidence for $p \bar{p}$ threshold enhancements was found in the reactions $ψ (2 S) \to X p \bar{p}$ , where $X = γ$ , $π^{0}$ , $η$ . We do, however, find confirming evidence for a $p \bar{p}$ threshold enhancement in $J / ψ \to γ p \bar{p}$ as previously reported by BES.