First observation of exclusive $\hat{I}\yen (1S)$ and $\hat{I}\yen (2S)$ decays into light hadrons

Abstract

Using samples of 102 million $\hat{I}\yen (1S)$ and 158 million $\hat{I}\yen (2S)$ events collected with the Belle detector, we study exclusive hadronic decays of these two bottomonium resonances to the three-body final states $\ddot{I}•K^{+}{K}^{-}$, $\ddot{I}‰\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ and $K^{\ast 0}(892)K^{-}\ddot{I}{€}^{+}$, and to the two-body Vector-Tensor ($\ddot{I}•f_2^{\prime }(1525)$, $\ddot{I}‰f_2(1270)$, $\ddot{I}a_2(1320)$ and $K^{\ast 0}(892){\bar{K}}_2^{\ast 0}(1430)$) and Axial-vector-Pseudoscalar ($K_1(1270{)}^{+}{K}^{-}$, $K_1(1400{)}^{+}{K}^{-}$ and $b_1(1235{)}^{+}\ddot{I}{€}^{-}$) pairs. Signals are observed for the first time in the $\hat{I}\yen (1S)\to \ddot{I}•K^{+}{K}^{-}$, $\ddot{I}‰\ddot{I}{€}^{+}\ddot{I}{€}^{-}$, $K^{\ast 0}{K}^{-}\ddot{I}{€}^{+}$, $K^{\ast 0}{K}_2^{\ast 0}$ and $\hat{I}\yen (2S)\to \ddot{I}•K^{+}{K}^{-}$, $K^{\ast 0}{K}^{-}\ddot{I}{€}^{+}$ 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 $3\ddot{I}ƒ$. The ratios of the branching fractions of $\hat{I}\yen (2S)$ and $\hat{I}\yen (1S)$ decays into the same final state are used to test a perturbative QCD prediction for OZI suppressed bottomonium decays.

7 pages, 5 figures, 1 table, accepted for publication as a Rapid Communication in Physical Review D