Using samples of 102 million ${\rm Y}(1S)$ and 158 million ${\rm Y}(2S)$ events collected with the Belle detector, we study exclusive hadronic decays of these two bottomonium resonances to $K_S^0{K}^{+}{\pi }^{-}$ and charge-conjugate (c.c.) states, ${\pi }^{+}{\pi }^{-}{\pi }^0{\pi }^0$, and ${\pi }^{+}{\pi }^{-}{\pi }^0$, and to the two-body Vector-Pseudoscalar ($K^{*}(892{)}^0{\overline{K}}^0+\mathrm{c}.\mathrm{c}.$, $K^{*}(892{)}^{-}{K}^{+}+\mathrm{c}.\mathrm{c}.$, $\omega {\pi }^0$, and $\rho \pi$) final states. For the first time, signals are observed in the modes ${\rm Y}(1S)\to K_S^0{K}^{+}{\pi }^{-}+\mathrm{c}.\mathrm{c}.$, ${\pi }^{+}{\pi }^{-}{\pi }^0{\pi }^0$, and ${\rm Y}(2S)\to {\pi }^{+}{\pi }^{-}{\pi }^0{\pi }^0$, and evidence is found for the modes ${\rm Y}(1S)\to {\pi }^{+}{\pi }^{-}{\pi }^0$, $K^{*}(892{)}^0{\overline{K}}^0+\mathrm{c}.\mathrm{c}.$, and ${\rm Y}(2S)\to K_S^0{K}^{+}{\pi }^{-}+\mathrm{c}.\mathrm{c}.$ Branching fractions are measured for all the processes, while 90% confidence level upper limits on the branching fractions are also set for the modes with a statistical significance of less than $3\sigma$. The ratios of the branching fractions of ${\rm Y}(2S)$ and ${\rm Y}(1S)$ decays into the same final state are used to test a perturbative QCD prediction for Okubo-Zweig-Iizuka-suppressed bottomonium decays.

• Received 25 May 2013

DOI:https://doi.org/10.1103/PhysRevD.88.011102