Production of the $Z_b^{(\prime)}$ states from the $\Upsilon(5S,6S)$ decays

TL;DR

This paper explores how the $Z_b^{( ext{prime})}$ states are produced from $S$ and $S$ decays, highlighting the dominant role of loops involving broad bottom meson resonances and predicting measurable branching ratios.

Contribution

It introduces a novel mechanism involving broad bottom meson loops as the main production pathway for $Z_b^{( ext{prime})}$ states in $S$ and $S$ decays, with predictions for future experiments.

Findings

Loop contributions with all ground state bottom mesons are negligible.

Loops with broad $B_0^*$ or $B_1'$ resonances dominate the production.

Predicted branching ratios for $S$ decays can be tested at Belle-II.

Abstract

In the present work, we investigate the production mechanism of the $Z_b(10610)$ and $Z_b(10650)$ states from the $\Upsilon(5S,6S)$ decays. Two types of bottom-meson loops are discussed. We show that the loop contributions with all intermediate states being the $S$-wave ground state bottom mesons are negligible, while the loops with one bottom meson being the broad $B_0^\ast$ or $B_1^\prime$ resonance could provide the dominant contributions to the $\Upsilon(5S) \to Z_b^{(\prime)} \pi$. It is found that such a mechanism is not suppressed by the large width of the $B_0/B_1'$ resonance. In addition, we also estimate the branching ratios for the $\Upsilon(6S) \to Z_b^{(\prime)} \pi$ which could be tested by future precise measurements at Belle-II.