Observation of e+e−→ηY(2175) at center-of-mass energies above 3.7 GeV

Le résumé fourni par la source

The state $Y(2175)$ is observed in the process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\eta}Y(2175)$ with a statistical significance larger than 10 standard deviations using the data collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies between 3.7 and 4.6 GeV. This is the first observation of the $Y(2175)$ in this process. The mass and width of the $Y(2175)$ are determined to be $(2135\ifmmode\pm\else\textpm\fi{}8\ifmmode\pm\else\textpm\fi{}9)\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ and $(104\ifmmode\pm\else\textpm\fi{}24\ifmmode\pm\else\textpm\fi{}12)\text{ }\text{ }\mathrm{MeV}$, respectively, and the production cross section ($\ensuremath{\sigma}$) of ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\eta}Y(2175)\ensuremath{\rightarrow}\ensuremath{\eta}\ensuremath{\phi}{f}_{0}(980)\ensuremath{\rightarrow}\ensuremath{\eta}\ensuremath{\phi}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ is at the several hundred femtobarn level. No significant signal for the process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\eta}}^{\ensuremath{'}}Y(2175)$ is observed and the upper limit on $\ensuremath{\sigma}({e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\eta}}^{\ensuremath{'}}Y(2175))/\ensuremath{\sigma}({e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\eta}Y(2175))$ is estimated to be 0.43 at the 90% confidence level. We also search for $\ensuremath{\psi}(3686)\ensuremath{\rightarrow}\ensuremath{\eta}Y(2175)$. No significant signal is observed, indicating a strong suppression relative to the corresponding $J/\ensuremath{\psi}$ decay, in violation of the ``12% rule''.

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