Measurement of $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}ˆ(3686)$ from 4.008 to 4.600$\sim$GeV and observation of a charged structure in the $\ddot{I}{€}^{\pm }\ddot{I}ˆ(3686)$ mass spectrum

Abstract

We study the process $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}ˆ(3686)$ using 5.1 $f{b}^{-1}$ of data collected at 16 center-of-mass energy ($\sqrt{s}$) points from 4.008 to 4.600$\sim$GeV by the BESIII detector operating at the BEPCII collider. The measured Born cross sections for $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}ˆ(3686)$ 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\pm 7.4\pm 1.4$$\sim$MeV/$c^2$ and $\hat{I}“=80.1\pm 24.6\pm 2.9$$\sim$MeV, and the second has $M=4383.8\pm 4.2\pm 0.8$$\sim$MeV/c${}^2$ and $\hat{I}“=84.2\pm 12.5\pm 2.1$$\sim$MeV, where the first errors are statistical and the second systematic. The lower-mass resonance is observed in the process $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}ˆ(3686)$ for the first time with a statistical significance of $5.8\ddot{I}ƒ$. A charged charmonium-like structure is observed in the $\ddot{I}{€}^{\pm }\ddot{I}ˆ(3686)$ invariant mass spectrum for data at $\sqrt{s}=4.416$GeV. A fit with an $S$-wave Breit-Wigner function yields a mass $M=4032.1\pm 2.4$~$MeV$^{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.