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arXiv · 1512.03583

Effect of $Z_b$ states on $\Upsilon(3S)\to\Upsilon(1S)\pi\pi$ decays

Yun-Hua Chen·Johanna T. Daub·Feng-Kun Guo·Bastian Kubis·Ulf-G. Meißner·Bing-Song Zou
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Abstract

Within the framework of dispersion theory, we analyze the dipion transitions between the lightest $\Upsilon$ states, $\Upsilon(nS) \rightarrow \Upsilon(mS) \pi\pi$ with $m < n \leq 3$. In particular, we consider the possible effects of two intermediate bottomoniumlike exotic states $Z_b(10610)$ and $Z_b(10650)$. The $\pi\pi$ rescattering effects are taken into account in a model-independent way using dispersion theory. We confirm that matching the dispersive representation to the leading chiral amplitude alone cannot reproduce the peculiar two-peak $\pi\pi$ mass spectrum of the decay $\Upsilon(3S) \rightarrow \Upsilon(1S) \pi\pi$. The existence of the bottomoniumlike $Z_b$ states can naturally explain this anomaly. We also point out the necessity of a proper extraction of the coupling strengths for the $Z_b$ states to $\Upsilon(nS)\pi$, which is only possible if a Flatt\'e-like parametrization is used in the data analysis for the $Z_b$ states.

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Yun-Hua Chen, Johanna T. Daub, Feng-Kun Guo, Bastian Kubis, Ulf-G. Meißner, Bing-Song Zou. 2015-12-11. Effect of $Z_b$ states on $\Upsilon(3S)\to\Upsilon(1S)\pi\pi$ decays. https://doi.org/10.1103/physrevd.93.034030

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