Contribution of $Z_b$ resonances to ${\rm Y}(5S)\to \pi \pi \pi {\chi }_b$

Abstract

We discuss the recently presented Belle results on the decays ${\rm Y}(5S)\to \pi \pi \pi {\chi }_{bJ}(1P)$. The data indicate that in addition to the $\omega$ emission, ${\rm Y}(5S)\to \omega {\chi }_{bJ}$, 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 ${\rm Y}(5S)\to \pi Z_b\to \pi \rho {\chi }_b$ 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.

Comments: 7 pages, 1 figure