Measurement of the $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0$ cross section from 0.7 GeV to 3.0 GeV via initial-state radiation

Abstract

The cross section of the process $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0$ is measured with a precision of 1.6% to 25% in the energy range between $0.7$ and 3.0 GeV using the Initial State Radiation method. A data set with an integrated luminosity of $2.93$fb${}^{-1}$ taken at the center-of-mass energy of $\sqrt{s}=3.773$GeV with the BESIII detector at the BEPCII collider is used. The product branching fractions for $\ddot{I}‰$, $\ddot{I}•$, $\ddot{I}‰(1420)$, and $\ddot{I}‰(1650)$ are measured to be $\mathcal{B}(\ddot{I}‰\to e^{+}{e}^{-})\times \mathcal{B}(\ddot{I}‰\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0)=(6.94\pm 0.08\pm 0.16)\times 10^{-5}$, $\mathcal{B}(\ddot{I}•\to e^{+}{e}^{-})\times \mathcal{B}(\ddot{I}•\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0)=(4.20\pm 0.08\pm 0.19)\times 10^{-5}$, $\mathcal{B}(\ddot{I}‰(1420)\to e^{+}{e}^{-})\times \mathcal{B}(\ddot{I}‰(1420)\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0)=(0.84\pm 0.09\pm 0.09)\times 10^{-6}$, and $\mathcal{B}(\ddot{I}‰(1650)\to e^{+}{e}^{)}\times \mathcal{B}(\ddot{I}‰(1650)\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0)=(1.14\pm 0.15\pm 0.15)\times 10^{-6}$, respectively. The branching fraction $\mathcal{B}(J/\ddot{I}ˆ\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0)$ is measured to be $(2.188\pm 0.024\pm 0.024\pm 0.040(\hat{I}{“}_{ee}^{J/\ddot{I}ˆ}))\%$, where $\hat{I}{“}_{ee}^{J/\ddot{I}ˆ}$ is the dileptonic width of $J/\ddot{I}ˆ$. The first errors are of statistical, the second and third ones of systematic nature.