Study of $\hat{I}\yen (10753)$ decays to $\ddot{I}{€}^{+}\ddot{I}{€}^{-}\hat{I}\yen (nS)$ final states at Belle II

Abstract

We present an analysis of the process $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\hat{I}\yen (nS)$ (where $n$ = 1, 2, or 3) reconstructed in $19.6$ $\mathrm{f}{\mathrm{b}}^{-1}$ of Belle II data during a special run of the SuperKEKB collider at four energy points near the peak of the $\hat{I}\yen (10753)$ resonance. By analyzing the mass distribution of the $\ddot{I}{€}^{+}\ddot{I}{€}^{-}\hat{I}\yen (nS)$ system and the Born cross sections of the $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\hat{I}\yen (nS)$ process, we report the first observation of $\hat{I}\yen (10753)$ decays to the $\ddot{I}{€}^{+}\ddot{I}{€}^{-}\hat{I}\yen (1S)$ and $\ddot{I}{€}^{+}\ddot{I}{€}^{-}\hat{I}\yen (2S)$ final states, and find no evidence for decays to $\ddot{I}{€}^{+}\ddot{I}{€}^{-}\hat{I}\yen (3S)$. Possible intermediate states in the $\ddot{I}{€}^{+}\ddot{I}{€}^{-}\hat{I}\yen (1S,2S)$ transitions are also investigated, and no evidence for decays proceeding via the $\ddot{I}{€}^{\mp }{Z}_b^{\pm }$ or $f_0(980)\hat{I}\yen (nS)$ intermediate states is found. We measure Born cross sections for the $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\hat{I}\yen (nS)$ process that, combined with results from Belle, improve the precision of measurements of the $\hat{I}\yen (10753)$ mass and width by nearly a factor of two to $(10756.3\pm 2.7\pm 0.6)$ MeV/$c^2$ and $(29.7\pm 8.5\pm 1.1)$ MeV, respectively. The relative ratios of the Born cross sections at the $\hat{I}\yen (10753)$ resonance peak are also reported for the first time.