Measurement of the cross sections for $e^{+}{e}^{-}\to \hat{I}\cdot \ddot{I}{€}^{+}\ddot{I}{€}^{-}$ at center-of-mass energies between 2.00 and 3.08 GeV

Abstract

Using data samples collected at center-of-mass energies between 2.000 and 3.080 GeV with the BESIII detector operating at the BEPCII collider, a partial-wave analysis is performed on the process $e^{+}{e}^{-}\to \hat{I}\cdot \ddot{I}{€}^{+}\ddot{I}{€}^{-}$. In addition to the dominant $e^{+}{e}^{-}\to \ddot{I}\hat{I}\cdot$ component, the $e^{+}{e}^{-}\to a_2(1320)\ddot{I}€$ process is also sizeable, contributing up to 24% of the total reaction. The measured cross sections of the process $e^{+}{e}^{-}\to \hat{I}\cdot \ddot{I}{€}^{+}\ddot{I}{€}^{-}$ are systematically higher than those of BaBar by more than $3\ddot{I}ƒ$ at center-of-mass energies between 2.000 and 2.300 GeV. In the cross section lineshape for $e^{+}{e}^{-}\to a_2(1320)\ddot{I}€$, a resonant structure is observed with a significance of $5.5\ddot{I}ƒ$, with $M=(2044\pm 31\pm 4)$ MeV/$c^2$, $\hat{I}“=(163\pm 69\pm 24)$ MeV and ${\mathcal{B}}_{\mathcal{R}}\cdot \hat{I}{“}_{e^{+}{e}^{-}}^R=(34.6\pm 17.1\pm 6.0)$ eV or $(137.1\pm 73.3\pm 2.1)$ eV. In the cross section lineshape for $e^{+}{e}^{-}\to \ddot{I}\hat{I}\cdot$, an evidence of a dip structure around 2180 MeV/$c^2$ is observed with statistical significance of $3.0\ddot{I}ƒ$.