Spin-Parity Analysis of ppbar Mass Threshold Structure in J/psi and psi' Radiative Decays

Abstract

A partial wave analysis of the $p\bar{p}$ mass-threshold enhancement in the reaction $J/\psi \to \gamma p\bar{p}$ is used to determine: its $J^{PC}$ quantum numbers to be $0^{-+}$; its peak mass to be below threshold at $M=1832_{-5}^{+19}{(stat.)}_{-17}^{+18}(syst.)\pm 19(\mathrm{model})\mathrm{MeV}/c^2$; and its total width to be $\Gamma <76\mathrm{MeV}/c^2$ at the 90% C.L. The product branching ratio is measured to be $B(J/\psi \to \gamma X(p\bar{p}))B(X(p\bar{p})\to p\bar{p})=(9.0_{-1.1}^{+0.4}{(stat.)}_{-5.0}^{+1.5}(syst.)\pm 2.3(\mathrm{model}))\times 10^{-5}$. A similar analysis performed on ${\psi }^{\prime }\to \gamma p\bar{p}$ decays shows, for the first time, the presence of a corresponding enhancement with a production rate relative to that for $J/\psi$ decays of $R=(5.08_{-0.45}^{+0.71}{(stat.)}_{-3.58}^{+0.67}(syst.)\pm 0.12(\mathrm{model}))$.

5 pages, 3 figures, submitted to Phys. Rev. Lett

References in corpus (5)

• Confirmation of the X(1835) and observation of the resonances X(2120) and X(2370) in J/psi->gamma pi^+pi^-eta'
• Study of psi(2S) Decays to gamma p bar{p}, pi^0 p bar{p} and eta p bar{p} and Search for p bar{p} Threshold Enhancements
• Measurement of the Matrix Element for the Decay ${\eta }^{\prime }\to \eta {\pi }^{+}{\pi }^{-}$
• Measurement of $\psip$ Radiative Decays
• A possible mechanism for producing the threshold enhancement in $J/\psi \to \gamma p\bar{p}$

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