Speaker
Prof.
Alexander Bondar
(Novosibirsk State University (RU))
Description
We report the results of the $R_b$ scan in the region from 10750 MeV to 11020 MeV in steps of 5 MeV. The scan data were collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. This result can be used to map the shape of the $\Upsilon(10860)$ and $\Upsilon(11020)$ resonances. The search for the tetraquark candidate $Y(10900)$ is also reported.
We report on the study of the hadronic transitions from the $\Upsilon(5S)$ to lower bottomonia using 121.4 fb$^{-1}$ data collected at the $\Upsilon(5S)$ resonance by the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. Decays of the $\Upsilon(5S)$ to the $\Upsilon(1D)\pi^+\pi^-$ and $\Upsilon(1,2S)\eta$ final states have been observed for the first time.
Recently, Belle observed the spin-singlet bottomonium states $h_b(1P)$ and $h_b(2P)$. Radiative transitions to the $\eta_b(1S)$ and $\eta_b(2S)$ are expected to account for a large fraction of the $h_b(nP)$ decays. We report on the measurement of the $\eta_b(1S)$ and $\eta_b(2S)$ parameters using these radiative transitions. We report the most precise measurement of the $\eta_b(1S)$ mass, first measurement of its width, first measurement of the $\eta_b(2S)$ mass, and first measurement of the branching fractions of the radiative transitions $h_b(nP)\rightarrow\eta_b(mS)\gamma$.
Recently, Belle observed two exotic resonances $Z_b(10510)$ and $Z_b(10560)$ produced in the $\Upsilon(5S)\rightarrow Z_b^+\pi^-$ transitions and decaying into the $\Upsilon(1S)\pi^+$, $\Upsilon(2S)\pi^+$, $\Upsilon(3S)\pi^+$, $h_b(1P)\pi^+$ and $h_b(2P)\pi^+$ final states. We report on further studies of these resonances.
Author
Prof.
Alexander Bondar
(Novosibirsk State University (RU))
