Observation of a resonant structure in $e^{+}{e}^{-}\to K^{+}{K}^{-}\ddot{I}{€}^0\ddot{I}{€}^0$

Abstract

Using $e^{+}{e}^{-}$ collision data samples with center-of-mass energies ranging from 2.000 to 2.644 GeV, collected by the BESIII detector at the BEPCII collider, and with a total integrated luminosity of 300 pb^{-1}, a partial-wave analysis is performed for the process $e^{+}{e}^{-}\to K^{+}{K}^{-}\ddot{I}{€}^0\ddot{I}{€}^0$. The total Born cross sections for the process $e^{+}{e}^{-}\to K^{+}{K}^{-}\ddot{I}{€}^0\ddot{I}{€}^0$, as well as the Born cross sections f or the subprocesses $e^{+}{e}^{-}\to \ddot{I}•\ddot{I}{€}^0\ddot{I}{€}^0$, $K^{+}(1460)K^{-}$, $K_1^{+}(1400)K^{-}$, $K_1^{+}(1270)K^{-}$ and $K^{\ast +}(892)K^{\ast -}(892)$, are measured versus the center-of-mass energy. The corresponding results for $e^{+}{e}^{-}\to K^{+}{K}^{-}\ddot{I}{€}^0\ddot{I}{€}^0$ and $\ddot{I}•\ddot{I}{€}^0\ddot{I}{€}^0$ are consistent with those of BaBar and have much improved precision.By analyzing the cross sections for the four subprocesses, $K^{+}(1460)K^{-}$, $K_1^{+}(1400)K^{-}$, $K_1^{+}(1270)K^{-}$ and $K^{\ast +}{K}^{\ast -}$, a structure with mass $M$ = (2126.5 $\pm$ 16.8 $\pm$ 12.4)~MeV/c^{2} and width $\hat{I}“$ = (106.9 $\pm$ 32.1 $\pm$ 28.1)~MeV is observed with an overall statistical significance of 6.3 $\ddot{I}ƒ$, although with very limited significance in the subprocesses $e^{+}{e}^{-}\to K_1^{+}(1270)K^{-}$ and $K^{\ast +}(892)K^{\ast -}(892)$. The resonant parameters of the observed structure suggest it can be identified with the $\ddot{I}•(2170)$, thus the results provide valuable input to the internal nature of the $\ddot{I}•(2170)$.