Evidence of $h_b(\text{2P})\to \mathrm{{\rm Y}}(\text{1S})\eta$ decay and search for $h_b(\text{1P,2P})\to \mathrm{{\rm Y}}(\text{1S}){\pi }^0$ with the Belle detector

We report the first evidence for the $h_b(\text{2P})\to \mathrm{{\rm Y}}(\text{1S})\eta$ transition with a significance of $3.5$ standard deviations. The decay branching fraction is measured to be $\mathcal{B}[h_b(\text{2P})\to \mathrm{{\rm Y}}(\text{1S})\eta ]=(7.1{}_{-3.2}^{+3.7}\pm 0.8)\times {10}^{-3}$, which is noticeably smaller than expected. We also set upper limits on ${\pi }^0$ transitions of $\mathcal{B}[h_b(\text{2P})\to \mathrm{{\rm Y}}(\text{1S}){\pi }^0]<1.8\times {10}^{-3}$, and $\mathcal{B}[h_b(\text{1P})\to \mathrm{{\rm Y}}(\text{1S}){\pi }^0]<1.8\times {10}^{-3}$, at the $90\mathrm{\%}$ confidence level. These results are obtained with a $131.4$~fb${}^{-1}$ data sample collected near the $\mathrm{{\rm Y}}(\text{5S})$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider.