Measurement of exclusive Upsilon(1S) and Upsilon(2S) decays into vector-pseudoscalar final states

Abstract

Using samples of 102 million Υ(1S) and 158 million Υ(2S) events collected with the Belle detector, we study exclusive hadronic decays of these two bottomonium resonances to KS0K+π- and charge-conjugate (c.c.) states, π+π-π0π0, and π+π-π0, and to the two-body Vector-Pseudoscalar (K*(892)0K¯0+c.c., K*(892)-K++c.c., ωπ0, and ρπ) final states. For the first time, signals are observed in the modes Υ(1S)→KS0K+π-+c.c., π+π-π0π0, and Υ(2S)→π+π-π0π0, and evidence is found for the modes Υ(1S)→π+π-π0, K*(892)0K¯0+c.c., and Υ(2S)→KS0K+π-+c.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 3σ. The ratios of the branching fractions of Υ(2S) and Υ(1S) decays into the same final state are used to test a perturbative QCD prediction for Okubo-Zweig-Iizuka-suppressed bottomonium decays.