Speaker
Description
We report the first measurement of exclusive cross sections for $e^{+}e^{-} \to B\bar{B}$, $e^{+}e^{-} \to B\bar{B}^{*}$, and $e^{+}e^{-} \to B^{*}\bar{B}^{*}$ in the energy range from $10.63$ to $11.02\,{\rm GeV}$. The $B$ mesons are fully reconstructed in a large number of hadronic final states, and the three channels are distinguished using the beam-energy-constrained mass variable. For each channel, the cross section shows an oscillatory behavior, with multiple maxima and minima. The final results on $\Upsilon(5S) \to \Upsilon(1S,2S) \eta$ and $\Upsilon(5S) \to \Upsilon(1S) \eta^{\prime}$ branching fractions are also presented. In addition, we report a search for the $\chi_{bJ}(nP)$ bottomonium states at Belle. The $P$-wave states are reconstructed in decays to the $\Upsilon(1S)$ with the emission of an $\omega$ meson. The transitions of the $n=2$ triplet states provide a unique laboratory to study QCD, as the kinematic threshold for production of an $\omega$ and $\Upsilon(1S)$ meson lies between the $J=0$ and $J=1$ states. A search for the $\chi_{bJ}(3P)$ states in radiative transitions from $\Upsilon(4S)$ is also performed. All these results are based on data collected by the Belle experiment at the KEKB asymmetric-energy $e^+e^-$ collider.
| Collaboration / Activity | Belle |
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