Improved measurement of Born cross sections for $\ddot{I}{‡}_{bJ}\ddot{I}‰$ and $\ddot{I}{‡}_{bJ}(\ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0{)}_{\mathrm{non}-\ddot{\mathrm{I}}‰}$ ($J$ = 0, 1, 2) at Belle and Belle II

Abstract

We study the processes $\ddot{I}{‡}_{bJ}\ddot{I}‰$ and $\ddot{I}{‡}_{bJ}(\ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0{)}_{\mathrm{non}-\ddot{\mathrm{I}}‰}$ ($J$ = 0, 1, 2) at center-of-mass energies $\sqrt{s}$ from 10.73 to 11.02 GeV using a $142.5{\mathrm{fb}}^{-1}$ data sample collected with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider; and at $\sqrt{s}\sim 10.75$ GeV using a $19.8{\mathrm{fb}}^{-1}$ sample collected with Belle II at SuperKEKB. We find that the $\hat{I}\yen (10753)$ state decays into $\ddot{I}{‡}_{bJ}\ddot{I}‰$ but not into $\ddot{I}{‡}_{bJ}(\ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0{)}_{\mathrm{non}-\ddot{\mathrm{I}}‰}$, while the $\hat{I}\yen (10860)$ state, in contrast, decays into $\ddot{I}{‡}_{bJ}(\ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0{)}_{\mathrm{non}-\ddot{\mathrm{I}}‰}$ but not into $\ddot{I}{‡}_{bJ}\ddot{I}‰$. The mass and width of the $\hat{I}\yen (10753)$ state are measured to be $(10756.1\pm 3.4(stat.)\pm 2.7(syst.))$ MeV/$c^2$ and $(32.2\pm 11.3(stat.)\pm 14.9(syst.))$ MeV. The products of the partial width to $e^{+}{e}^{-}$ and branching fractions for $\hat{I}\yen (10753)\to \ddot{I}{‡}_{b1}\ddot{I}‰$ and $\hat{I}\yen (10753)\to \ddot{I}{‡}_{b2}\ddot{I}‰$ are ($1.57\pm 0.27(stat.)\pm 0.22(syst.)$) eV and ($1.39\pm 0.41(stat.)\pm 0.33(syst.)$) eV.

Belle II Preprint 2025-003; KEK Preprint 2024-52