Improved measurement of Born cross sections for χ₁₉ω and χ₁₉ (π^+π^−π^0) ₍₎₍−⏨ (J = 0, 1, 2) at Belle and Belle II

We study the processes χ₁₉ω and χ₁₉ (π^+π^−π^0) ₍₎₍−⏨ (J = 0, 1, 2) at center-of-mass energies s from 10. 73 to 11. 02 GeV using a 142. 5 fb^−1 data sample collected with the Belle detector at the KEKB asymmetric-energy e^+e^− collider; and at s 10. 75 GeV using a 19. 8 fb^−1 sample collected with Belle II at SuperKEKB. We find that the Υ (10753) state decays into χ₁₉ω but not into χ₁₉ (π^+π^−π^0) ₍₎₍−⏨, while the Υ (10860) state, in contrast, decays into χ₁₉ (π^+π^−π^0) ₍₎₍−⏨ but not into χ₁₉ω. The mass and width of the Υ (10753) state are measured to be (10756. 1 ± 3. 4 (stat. ) ± 2. 7 (syst. ) ) MeV/c^2 and (32. 2 ± 11. 3 (stat. ) ± 14. 9 (syst. ) ) MeV. The products of the partial width to e^+e^− and branching fractions for Υ (10753) → χ₁₁ω and Υ (10753) → χ₁₂ω are (1. 57 ± 0. 27 (stat. ) ± 0. 22 (syst. ) ) eV and (1. 39 ± 0. 41 (stat. ) ± 0. 33 (syst. ) ) eV. graphic not available: see fulltext