Measurement of e+e−→π+π−ψ(3686) from 4.008 to 4.600 GeV and observation of a charged structure in the π±ψ(3686) mass spectrum

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We study the process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\psi}(3686)$ using $5.1\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data collected at 16 center-of-mass energy ($\sqrt{s}$) points from 4.008 to 4.600 GeV by the BESIII detector operating at the BEPCII collider. The measured Born cross sections for ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\psi}(3686)$ are consistent with previous results, but with much improved precision. A fit to the cross section shows contributions from two structures: the first has $M=4209.5\ifmmode\pm\else\textpm\fi{}7.4\ifmmode\pm\else\textpm\fi{}1.4\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ and $\mathrm{\ensuremath{\Gamma}}=80.1\ifmmode\pm\else\textpm\fi{}24.6\ifmmode\pm\else\textpm\fi{}2.9\text{ }\text{ }\mathrm{MeV}$, and the second has $M=4383.8\ifmmode\pm\else\textpm\fi{}4.2\ifmmode\pm\else\textpm\fi{}0.8\text{ }\text{ }\mathrm{MeV}/{\mathrm{c}}^{2}$ and $\mathrm{\ensuremath{\Gamma}}=84.2\ifmmode\pm\else\textpm\fi{}12.5\ifmmode\pm\else\textpm\fi{}2.1\text{ }\text{ }\mathrm{MeV}$, where the first errors are statistical and the second systematic. The lower-mass resonance is observed in the process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\psi}(3686)$ for the first time with a statistical significance of $5.8\ensuremath{\sigma}$. A charged charmoniumlike structure is observed in the ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\psi}(3686)$ invariant mass spectrum for data at $\sqrt{s}=4.416\text{ }\text{ }\mathrm{GeV}$. A fit with an $S$-wave Breit-Wigner function yields a mass $M=4032.1\ifmmode\pm\else\textpm\fi{}2.4\text{ }\text{ }\mathrm{MeV}/{c}^{2}$, where the errors are statistical only. However, there are still unresolved discrepancies between the fit model and data. The width of the intermediate state varies in a wide range for different kinematic regions within the data set. Therefore, no simple interpretation of the data has been found, and a future data sample with larger statistics and more theoretical input will be required to better understand this issue.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.