Study of $e^{+}{e}^{-}\to h^{+}{h}^{-}J/\ddot{I}ˆ(h=\ddot{I}€,K,p)$ via initial-state radiation at Belle~II

Abstract

Using a data sample of 427.9 fb${}^{-1}$ collected by the Belle~II detector at or near the $\hat{I}\yen (4S)$ and $\hat{I}\yen (10753)$ resonances, the cross sections for $e^{+}{e}^{-}\to h^{+}{h}^{-}J/\ddot{I}ˆ$ $(h=\ddot{I}€/K/p)$ at center-of-mass energies ranging from 3.8 GeV or the production threshold to 5.5/6.0/7.0 GeV have been measured via initial-state radiation. The cross sections for the processes $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}J/\ddot{I}ˆ$ and $e^{+}{e}^{-}\to K^{+}{K}^{-}J/\ddot{I}ˆ$ are consistent with previously published results. The cross sections for these channels obtained by combining with previous Belle results are also given. The process $e^{+}{e}^{-}\to p\bar{p}J/\ddot{I}ˆ$ is investigated for the first time. The yields are small and no significant structure is observed in the cross section versus energy. Searches for vector charmonium-like states in the $h^{+}{h}^{-}J/\ddot{I}ˆ$ systems, and for associated intermediate states in the $h^{\pm }J/\ddot{I}ˆ$ systems, are also presented.

Belle II Preprint: 2026-002 KEK Preprint: 2025-42