Evidence of hb(2P) → Υ(1S)η decay and search for hb(1P,2P) → Υ(1S)π⁰ with the Belle detector

We report the first evidence for the hb(2P) → Υ(1S)η transition with a significance of $3.5$ standard deviations. The decay branching fraction is measured to be B[hb(2P) → Υ(1S)η]=(7.1 ~+3.7 -3.2± 0.8)×10⁻³, which is noticeably smaller than expected. We also set upper limits on π⁰ transitions of B[hb(2P) → Υ(1S)π⁰] < 1.8×10⁻³, and B[hb(1P)→ Υ(1S)π⁰] < 1.8×10⁻³, at the $90%$ confidence level. These results are obtained with a $131.4$~fb⁻¹ data sample collected near the Υ(5S) resonance with the Belle detector at the KEKB asymmetric-energy e⁺e⁻ collider.