Production ofJ/ψ and ψ(2S) mesons inπ−Be collisions at 515 GeV/c

Citations Over TimeTop 10% of 1996 papers

Abstract

We have studied the production of J/\ensuremath{\psi} and \ensuremath{\psi}(2S) charmonium mesons in 515 GeV/c ${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$Be collisions in the Feynman-x range 0.1${\mathit{x}}_{\mathit{F}}$0.8. J/\ensuremath{\psi} mesons were detected via their decay into ${\mathrm{\ensuremath{\mu}}}^{+}$${\mathrm{\ensuremath{\mu}}}^{\mathrm{\ensuremath{-}}}$, and \ensuremath{\psi}(2S) mesons were studied in both the ${\mathrm{\ensuremath{\mu}}}^{+}$${\mathrm{\ensuremath{\mu}}}^{\mathrm{\ensuremath{-}}}$ and J/\ensuremath{\psi}${\mathrm{\ensuremath{\pi}}}^{+}$${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$ decay modes. J/\ensuremath{\psi} differential cross sections have been measured as functions of ${\mathit{x}}_{\mathit{F}}$,${\mathit{p}}_{\mathit{T}}^{2}$, and the cosine of the Gottfried-Jackson decay angle. We measure an inclusive J/\ensuremath{\psi} cross section of B(J/\ensuremath{\psi}\ensuremath{\rightarrow}${\mathrm{\ensuremath{\mu}}}^{+}$${\mathrm{\ensuremath{\mu}}}^{\mathrm{\ensuremath{-}}}$)\ensuremath{\sigma}(${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$Be\ensuremath{\rightarrow}J/\ensuremath{\psi}+X)/A= [9.3\ifmmode\pm\else\textpm\fi{}0.1(stat)\ifmmode\pm\else\textpm\fi{}1.1(syst)] nb/nucleon for J/\ensuremath{\psi} ${\mathit{x}}_{\mathit{F}}$\ensuremath{\gtrsim}0.1. Our results are compared with those from other experiments performed at lower beam energies. We also measure the differential \ensuremath{\psi}(2S) cross section as a function of both ${\mathit{x}}_{\mathit{F}}$ and ${\mathit{p}}_{\mathit{T}}^{2}$, and a \ensuremath{\psi}(2S) inclusive cross section of B(\ensuremath{\psi}(2S)\ensuremath{\rightarrow}J/\ensuremath{\psi}${\mathrm{\ensuremath{\pi}}}^{+}$${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$)\ensuremath{\sigma}(${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$Be\ensuremath{\rightarrow}\ensuremath{\psi}(2S)+X)/A=[7. 4\ifmmode\pm\else\textpm\fi{}1.5(stat)\ifmmode\pm\else\textpm\fi{}1.2(syst)] nb/nucleon for \ensuremath{\psi}(2S) ${\mathit{x}}_{\mathit{F}}$\ensuremath{\gtrsim}0.1. The fraction of the inclusive J/\ensuremath{\psi} yield due to \ensuremath{\psi}(2S) meson decays is 0.083\ifmmode\pm\else\textpm\fi{}0.017(stat) \ifmmode\pm\else\textpm\fi{}0.013(syst), and the observed ratio of \ensuremath{\psi}(2S) decay rates is B(\ensuremath{\psi}(2S)\ensuremath{\rightarrow}J/\ensuremath{\psi}${\mathrm{\ensuremath{\pi}}}^{+}$${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$)/B(\ensuremath{\psi}(2S)\ensuremath{\rightarrow}${\mathrm{\ensuremath{\mu}}}^{+}$${\mathrm{\ensuremath{\mu}}}^{\mathrm{\ensuremath{-}}}$) =30.2\ifmmode\pm\else\textpm\fi{}7.2(stat)\ifmmode\pm\else\textpm\fi{}6.8(syst). We have searched for production of ``hidden'' charm resonances decaying into either J/\ensuremath{\psi}${\mathrm{\ensuremath{\pi}}}^{\ifmmode\pm\else\textpm\fi{}}$,\ensuremath{\psi}(2S)${\mathrm{\ensuremath{\pi}}}^{\ifmmode\pm\else\textpm\fi{}}$, or J/\ensuremath{\psi}${\mathrm{\ensuremath{\pi}}}^{+}$${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$ systems, and report an upper limit of 3.1 nb/nucleon for the product of branching ratio and cross section for the recently reported enhancement at a J/\ensuremath{\psi}${\mathrm{\ensuremath{\pi}}}^{+}$${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$ mass of 3.836 GeV/${\mathit{c}}^{2}$. \textcopyright{} 1996 The American Physical Society.

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