Study of e+e−→π+π−π0ηc and evidence for Zc(3900)± decaying into ρ±ηc

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We study the reaction ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}{\ensuremath{\eta}}_{c}$ for the first time using data samples collected with the BESIII detector at center-of-mass energies $\sqrt{s}=4.226$, 4.258, 4.358, 4.416, and 4.600 GeV. Evidence of this process is found and the Born cross section ${\ensuremath{\sigma}}^{B}({e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}{\ensuremath{\eta}}_{c})$, excluding ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\omega}{\ensuremath{\eta}}_{c}$ and $\ensuremath{\eta}{\ensuremath{\eta}}_{c}$, is measured to be $({46}_{\ensuremath{-}11}^{+12}\ifmmode\pm\else\textpm\fi{}10)\text{ }\text{ }\mathrm{pb}$ at $\sqrt{s}=4.226\text{ }\text{ }\mathrm{GeV}$. Evidence for the decay ${Z}_{c}(3900{)}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\eta}}_{c}$ is reported at $\sqrt{s}=4.226\text{ }\text{ }\mathrm{GeV}$ with a significance of $3.9\ensuremath{\sigma}$, including systematic uncertainties, and the Born cross section times branching fraction ${\ensuremath{\sigma}}^{B}({e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{\mp}}{Z}_{c}(3900{)}^{\ifmmode\pm\else\textpm\fi{}})\ifmmode\times\else\texttimes\fi{}\mathcal{B}({Z}_{c}(3900{)}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\eta}}_{c})$ is measured to be $(48\ifmmode\pm\else\textpm\fi{}11\ifmmode\pm\else\textpm\fi{}11)\text{ }\text{ }\mathrm{pb}$, which indicates that ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{\mp}}{Z}_{c}(3900{)}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{\mp}}{\ensuremath{\rho}}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\eta}}_{c}$ dominates the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}{\ensuremath{\eta}}_{c}$ process. The ${Z}_{c}(3900{)}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\eta}}_{c}$ signal is not significant at the other center-of-mass energies and the corresponding upper limits are determined. In addition, no significant signal is observed in a search for ${Z}_{c}(4020{)}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\eta}}_{c}$ with the same data samples. The ratios ${R}_{{Z}_{c}(3900)}=\mathcal{B}({Z}_{c}(3900{)}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\eta}}_{c})/\mathcal{B}({Z}_{c}(3900{)}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}J/\ensuremath{\psi})$ and ${R}_{{Z}_{c}(4020)}=\mathcal{B}({Z}_{c}(4020{)}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\eta}}_{c})/\mathcal{B}({Z}_{c}(4020{)}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}{h}_{c})$ are obtained and compared with different theoretical interpretations of the ${Z}_{c}(3900{)}^{\ifmmode\pm\else\textpm\fi{}}$ and ${Z}_{c}(4020{)}^{\ifmmode\pm\else\textpm\fi{}}$.

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