The Belle and Belle II experiments have collected a 1. 6\, ab^-1 sample of e^+e^- collision data at center-of-mass energies near the (nS) resonances. We conduct searches for transitions from the spin-singlet hb (1P, 2P) states to the spin-triplet (1S) and ₁₉ (1P) states. We do not find evidence for the hb (1P, 2P) (1S) ⁰ and hb (2P) ₁₉ (1P) transitions. We find the first evidence for the hb (2P) (1S) transition. However, the measured branching fraction is lower than expected from related decays. Furthermore, we find evidence for P₂ ₂ ₒ (4459) ⁰ J/ decays in inclusive (1S, 2S) decays. This is the first evidence for an exotic state produced in (1S, 2S) decays.
Stefan Wallner (Fri,) studied this question.