Studies of Hadron Spectroscopy at Belle and Belle II

Abstract

The Belle and Belle II experiments have collected an 1.6 ab$^{-1}$ sample of $e^+e^-$ collision data at center-of-mass energies near the $\Upsilon(nS)$ resonances. In particular, the Belle II experiment collected a 19.2 fb$^{-1}$ sample of data at center-of-mass energies near the $\Upsilon(10753)$ resonance. We study the following processes: $e^+e^-\to \Upsilon(nS)\eta$, $e^+e^-\to \gamma X_b(\chi_{bJ}\pi^+\pi^-)$, and $e^{+}e^{-}\to\chi_{bJ}(1P) \gamma$. These results provide additional information about the nature of the $\Upsilon(10753)$ resonance and nearby structures. In addition, we measure the $B^{0}$ and $B^+$ meson mass difference, and $\sigma\left(e^+ e^-\to J/\psi p\bar{p}\right)$ over a range of center-of-mass energies accessed via initial-state radiation.