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.
Highlights
In the past decade, a growing number of new hadron states have been observed, which are dubbed as XYZ states in the heavy quarkonium mass regions
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 BÃ0 or B01 resonance could provide the dominant contributions to the Υð5SÞ → Zðb0Þπ
The bottom-meson loops should be important for the production of the Zb states
Summary
A growing number of new hadron states have been observed, which are dubbed as XYZ states in the heavy quarkonium mass regions (for recent reviews, we refer to Refs. [1,2,3,4,5,6,7,8,9,10]). We denote the velocity as vA and one has vA 1⁄4 0.12–0.14, which indicates that the corresponding amplitudes could be analyzed in a nonrelativistic framework Both the Υð5SÞBðÃÞBðÃÞ and BÃBðÃÞπ vertices are P-wave couplings. In these kinds of meson loops, all of the involved interaction vertices are S-wave coupling. Oð30Þ; ð3Þ assuming NA ∼ NB which is reasonable as long as all the couplings take natural values This means that the contribution from the B01BðÃÞ=BÃ0B à þ c:c: meson loops should be much larger than that from the S-wave bottom mesons, and can potentially lead to a large rate for the Zðb0Þ productions from the Υð5SÞ decays
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
