Observation of exclusive Y(1S) and Y(2S) decays into light hadrons
Using samples of 102 x 10(6) Gamma(1S) and 158 x 10(6) Gamma(2S) events collected with the Belle detector, we study exclusive hadronic decays of these two bottomonium resonances to the three-body final states phi K+K-, omega pi(+)pi(-) and K*(0)(892)K-pi(+), and to the two-body Vector-Tensor states (phi f'(2)(1525), omega f(2)(1270), rho a(2)(1320) and K*(0)(892)(K) over bar*(0)(2)(1430)) and Axial-vector-Pseudoscalar (K-1(1270)K-+(-), K-1(1400)K-+(-) and b(1)(1235)(+)pi(-)) states. Signals are observed for the first time in the Y(1S) -> phi K+K-, omega pi(+)pi(-), K*K-0(-)pi(+), K*K-0*(0)(2) Gamma(2S) -> phi K+K-, K*K-0(-)pi(+) decay modes. Branching fractions are determined for all the processes, while 90% confidence level upper limits are established on the branching fractions for the modes with a statistical significance less than 3 sigma. The ratios of the branching fractions of Gamma(2S) and Gamma(1S) decays into the same final state are used to test a perturbative QCD prediction for OZI-suppressed bottomonium decays.