Measurement of Born Cross Sections for $e^{+}{e}^{-}\to K^{+}\hat{I}{ž}^0\bar{\hat{I}}{\pounds }^{-}$ at $\sqrt{s}=3.51-4.95$ GeV and Observation of $\ddot{I}ˆ(3770)\to K^{+}\hat{I}{ž}^0\bar{\hat{I}}{\pounds }^{-}$

Abstract

Using 44.55 fb${}^{-1}$ of $e^{+}{e}^{-}$ collision data collected by the BESIII detector at the BEPCII collider, we report the first measurement of the Born cross sections for the $e^{+}{e}^{-}\to K^{+}\hat{I}{ž}^0\bar{\hat{I}}{\pounds }^{-}$ reaction at fifty-six center-of-mass energies between 3.51 and 4.95~GeV. A fit to the dressed cross sections reveals the first observation of the $\ddot{I}ˆ(3770)\to K^{+}\hat{I}{ž}^0\bar{\hat{I}}{\pounds }^{-}$ process, with a statistical significance of 6.0$\ddot{I}ƒ$ including systematic uncertainties. This result represents the first observation of charmless three-body baryonic decay of a vector charmonium state above the open-charm threshold. No significant signals for other charmonium(-like) states i.e., $\ddot{I}ˆ(4040)$, $\ddot{I}ˆ(4160)$, $Y(4230)$, $Y(4360)$, $\ddot{I}ˆ(4415)$, $Y(4500)$, $Y(4660)$ or $Y(4710)$ are observed, and the upper limits for the product of the branching fraction and the electronic partial width at the 90% confidence level for each assumed charmonium(-like) state are provided. Additionally, the ratios of Born cross sections between this work and the previous measurements of $e^{+}{e}^{-}\to K_S^0\bar{\hat{I}}{ž}^{-}\hat{I}{\pounds }^{-}$ and $K^{-}\bar{\hat{I}}{ž}^{+}\bar{\hat{I}}{\pounds }^0$ are provided, which can be used to validate theoretical predictions related to isospin symmetry.

13 pages, 3 figures, 1 End Matter