Contribution of $Z_b$ resonances to $Υ(5S) \to πππχ_b$

We discuss the recently presented Belle results on the decays $Υ(5S) \to πππχ_{bJ}(1P)$. The data indicate that in addition to the $ω$ emission, $Υ(5S) \to ωχ_{bJ}$, there is a significant non resonant background in the three pion spectrum. We suggest that a sizable fraction of this background may be associated with the cascade process $Υ(5S) \to πZ_b \to πρχ_b$ involving the $Z_b(10610)$ and $Z_b(10650)$ resonances. If confirmed by the data, this would be the first observation of transition from the $Z_b$ resonances to lower bottomonium with emission of a light meson state different from a single pion, which may provide a new input in understanding of the internal dynamics of these resonances.

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