Study of ${\chi }_{bJ}(2P)\to \omega {\rm Y}(1S)$ at Belle

Abstract

We report a study of the hadronic transitions ${\chi }_{bJ}(2P)\to \omega {\rm Y}(1S)$, with $\omega \to {\pi }^{+}{\pi }^{-}{\pi }^0$, using $28.2\times 10^6{\rm Y}(3S)$ mesons recorded by the Belle detector. We present the first evidence for the near--threshold transition ${\chi }_{b0}(2P)\to \omega {\rm Y}(1S)$, the analog of the near-threshold charm sector decay ${\chi }_{c1}(3872)\to \omega J/\psi$, with a branching fraction of $\mathcal{B}({\chi }_{b0}(2\mathcal{P})\to \omega {\rm Y}(1\mathcal{S}))=(0.55\pm 0.19\pm 0.07)\%$. We also obtain branching fractions of $\mathcal{B}({\chi }_{b1}(2\mathcal{P})\to \omega {\rm Y}(1\mathcal{S}))=(2.39{}_{-0.19}^{+0.20}\pm 0.24)\%$ and $\mathcal{B}({\chi }_{b2}(2\mathcal{P})\to \omega {\rm Y}(1\mathcal{S}))=(0.47{}_{-0.12}^{+0.13}\pm 0.06)\%$, confirming the measurement of the $\omega$ transitions of the $J=1,2P$--wave states. The ratio for the $J=2$ to $J=1$ transitions is also measured and found to differ by 3.3 standard deviations from the expected value in the QCD multipole expansion.

7 pages, 2 figures

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Cited by in corpus (1)

• Study of ${\chi }_{b1,2}(2P)\to \omega {\rm Y}(1S)$ transitions in ${\rm Y}(3S)\to \gamma {\chi }_{b1,2}(2P)$ decays at BaBar