Observation of $e^{+}{e}^{-}\to \hat{I}\cdot \hat{I}\yen (2S)$ and search for $e^{+}{e}^{-}\to \hat{I}\cdot \hat{I}\yen (1S),{\hat{I}}^3{X}_b$ at $\sqrt{s}$ near 10.75 GeV

Abstract

We present an analysis of the processes $e^{+}{e}^{-}\to \hat{I}\cdot \hat{I}\yen (1S)$, $\hat{I}\cdot \hat{I}\yen (2S)$, and ${\hat{I}}^3{X}_b$ with $X_b\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{‡}_{bJ},\ddot{I}{‡}_{bJ}\to {\hat{I}}^3\hat{I}\yen (1S)$ $(J=1,2)$ reconstructed from ${\hat{I}}^3{\hat{I}}^3\ddot{I}{€}^{+}\ddot{I}{€}^{-}{\ell }^{+}{\ell }^{-}(\ell =e,\hat{I}¼)$ final states in $19.6\mathrm{f}{\mathrm{b}}^{-1}$ of Belle II data collected at four energy points near the peak of the $\hat{I}\yen (10753)$ resonance. Here, $X_b$ is a hypothetical bottomonium-sector partner of the $X(3872)$. In the process $e^{+}{e}^{-}\to \hat{I}\cdot \hat{I}\yen (2S)$, we observe a signal with a significance that exceeds $6.0\ddot{I}ƒ$. Based on an analysis of the Born cross-section, the hypothesis that these events are associated solely with the production of the $\hat{I}\yen (5S)$ or $\hat{I}\yen (10753)$ resonances is rejected at the level of 3.6$\ddot{I}ƒ$. This suggests that the observed events are more likely to arise from a new state near the $B^{\ast }{\bar{B}}^{\ast }$ threshold or from a substantial continuum production. No significant signal is observed for $e^{+}{e}^{-}\to \hat{I}\cdot \hat{I}\yen (1S)$ or ${\hat{I}}^3{X}_b$. Upper limits on the Born cross sections for the processes $e^{+}{e}^{-}\to \hat{I}\cdot \hat{I}\yen (1S)$ and $e^{+}{e}^{-}\to {\hat{I}}^3{X}_b$ with $X_b\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{‡}_{bJ}$ are determined.