Abstract: | 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 $ks K^+ pi^-$ and charge-conjugate (c.c.)
states, $pi^+ pi^- pi^0 pi^0$, and $pi^+ pi^- pi^0$, and to the two-body
Vector-Pseudoscalar ($K^{ast}(892)^0ar{K}^0+ {
m c.c.}$,
$K^{ast}(892)^-K^+ + {
m c.c.}$, $omegapi^0$, and $
hopi$) final states.
For the first time, signals are observed in the modes $Upsilon(1S) o ks K^+
pi^- + {
m c.c.}$, $pi^+ pi^- pi^0 pi^0$, and $Upsilon(2S) o pi^+
pi^- pi^0 pi^0$, and evidence is found for the modes $Upsilon(1S) o pi^+
pi^- pi^0$, $K^{ast}(892)^0 ar{K}^0+ {
m c.c.}$, and $Upsilon(2S) o
ks K^+ pi^- + {
m c.c.}$ 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
$3sigma$. 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 decays. |