First observation of exclusive $\Upsilon(1S)$ and $\Upsilon(2S)$ decays into light hadrons

Source: arXiv


Using samples of 102 million $\Upsilon(1S)$ and 158 million $\Upsilon(2S)$
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^{\ast 0}(892) K^- \pi^+ $, and to the two-body
Vector-Tensor ($\phi f_2'(1525)$, $\omega f_2(1270)$, $\rho a_2(1320)$ 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)^+ \pi^- $) pairs. Signals
are observed for the first time in the $\Upsilon(1S) \to \phi K^+ K^-$, $\omega
\pi^+ \pi^-$, $K^{\ast 0} K^- \pi^+$, $K^{\ast0} K_2^{\ast 0}$ and
$\Upsilon(2S) \to \phi K^+ K^-$, $K^{\ast 0} K^- \pi^+$ 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 $\Upsilon(2S)$ and $\Upsilon(1S)$ decays into the same final state
are used to test a perturbative QCD prediction for OZI suppressed bottomonium

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Available from: Peter Križan, Dec 17, 2013