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Volume 316 - XXVI International Workshop on Deep-Inelastic Scattering and Related Subjects (DIS2018) - WG5: Physics with Heavy Flavours
Study of Quarkonia and Quarkonium-like States at Belle
S. Jia
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Pre-published on: 2018 September 20
Published on: 2018 November 23
We review recent results on quarkonia and quarkonium-like states from the Belle experiment. An enhancement of the transition $\Upsilon(4S)\to\eta\Upsilon(1S)$ with respect to the transition $\Upsilon(4S)\to\pi^{+}\pi^{-}\Upsilon(1S)$ is confirmed. The first observation of the processes $e^{+}e^{-}\to \eta \Upsilon_{J}(1D)$ in $e^+ e^-$ annihilation near $\Upsilon(5S)$ and $\Upsilon(4S)\to\eta^{\prime}\Upsilon(1S)$ is reported. The new state $X^{*}(3860)$ is clearly observed with a significance of 6.5$\sigma$ in the distribution of invariant mass of $D \bar {D}$. We search for charmonium-like states, including $X(3872)$ in the missing mass spectrum of $K^{+}$, $Y(4660)$ and its spin partner in the distribution of $\Lambda^{+}_{c}\Lambda^{-}_{c}$ invariant mass, and double $Z_{c}$ in $\Upsilon(1S,2S)$ decays and $e^+ e^-$ annihilation at $\sqrt{s} =$ 10.52, 10.58, and 10.867 GeV. No significant signals are observed in any of the studied modes, and the 90\% confidence level (C.L.) upper limits on their branching fractions or the Born cross sections are determined.
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