Study of $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0$ at $\sqrt{s}$ from 2.00 to 3.08 GeV at BESIII

Abstract

With the data samples taken at center-of-mass energies from 2.00 to 3.08 GeV with the BESIII detector at the BEPCII collider, a partial wave analysis on the $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0$ process is performed. The Born cross sections for $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0$ and its intermediate processes $e^{+}{e}^{-}\to \ddot{I}\ddot{I}€$ and $\ddot{I}(1450)\ddot{I}€$ are measured as functions of $\sqrt{s}$. The results for $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0$ are consistent with previous results measured with the initial state radiation method within one standard deviation, and improve the uncertainty by a factor of ten. By fitting the line shapes of the Born cross sections for the $e^{+}{e}^{-}\to \ddot{I}\ddot{I}€$ and $\ddot{I}(1450)\ddot{I}€$, a structure with mass $M=2119\pm 11\pm 15\mathrm{MeV}/c^2$ and width $\hat{I}“=69\pm 30\pm 5\mathrm{MeV}$ is observed with a significance of $5.9\ddot{I}ƒ$, where the first uncertainties are statistical and the second ones are systematic. This structure can be intepreteted as an excited $\ddot{I}‰$ state.