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Abstract

A combined fit is performed to the BABAR and Belle measurements of the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\psi}(2S)$ cross sections for center-of-mass energy between threshold and 5.5 GeV. The resonant parameters of the $Y(4360)$ and $Y(4660)$ are determined. The mass is ${4355}_{\ensuremath{-}10}^{+9}\ifmmode\pm\else\textpm\fi{}9\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ and the width is ${103}_{\ensuremath{-}15}^{+17}\ifmmode\pm\else\textpm\fi{}11\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ for the $Y(4360)$, and the mass is ${4661}_{\ensuremath{-}8}^{+9}\ifmmode\pm\else\textpm\fi{}6\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ and the width is ${42}_{\ensuremath{-}12}^{+17}\ifmmode\pm\else\textpm\fi{}6\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ for the $Y(4660)$. The production of the $Y(4260)$ in ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\psi}(2S)$ mode is found to be at $2\ensuremath{\sigma}$ level, and $\mathcal{B}(Y(4260)\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\psi}(2S))\ifmmode\cdot\else\textperiodcentered\fi{}{\ensuremath{\Gamma}}_{{e}^{+}{e}^{\ensuremath{-}}}$ is found to be less than $4.3\text{ }\text{ }\mathrm{eV}/{c}^{2}$ at the 90% confidence level, or equal to ${7.4}_{\ensuremath{-}1.7}^{+2.1}\text{ }\text{ }\mathrm{eV}/{c}^{2}$ depending on whether it interferes with the $Y(4360)$ constructively or destructively. This information will shed light on the understanding of the nature of the $Y$ states observed in initial state radiation processes.

Combined fit toBABARand Belle data one+e−→π+π−ψ(2S)

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Abstract

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