Observation of resonant contribution to the $e^{+}{e}^{-}\to \hat{I}{\text{c◯}}^{-}\bar{\hat{I}}{\text{c◯}}^{+}$ around 4.2 GeV and evidence of $\ddot{I}ˆ(3770)\to \hat{I}{\text{c◯}}^{-}\bar{\hat{I}}{\text{c◯}}^{+}$

Abstract

Using $e^{+}{e}^{-}$ collision data corresponding to a total integrated luminosity of 22.7 fb${}^{-1}$, collected at center-of-mass energies between 3.7 and 4.7 GeV with the BESIII detector, we present a measurement of energy-dependent cross sections and effective form factors for the process of $e^{+}{e}^{-}\to \hat{I}{\text{c◯}}^{-}\bar{\hat{I}}{\text{c◯}}^{+}$. By conducting a fit to the cross sections of $e^{+}{e}^{-}\to \hat{I}{\text{c◯}}^{-}\bar{\hat{I}}{\text{c◯}}^{+}$ considering the continuum and resonant contributions, a clear resonant structure in the spectrum around 4.2 GeV is observed for the first time with a statistical significance exceeding 10$\ddot{I}ƒ$, and it can be well described with the line shape of the $Y(4230)$ and $Y(4320)$ observed in $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}J/\ddot{I}ˆ$. Evidence for the decay $\ddot{I}ˆ(3770)\to \hat{I}{\text{c◯}}^{-}\bar{\hat{I}}{\text{c◯}}^{+}$ is observed with a statistical significance of 4.4$\ddot{I}ƒ$ by analyzing the measured cross sections together with earlier BESIII results, and the branching fraction is firstly measured to be $(4.0\pm 1.0\pm 0.6)$ $\times$ $10^{-5}$, where the first uncertainty is statistical and the second is systematic.

Major flaw in Section of fit of dressed cross section invalidates the main results