The nature of $Z_b$ states from a combined analysis of ${\rm Y}(5S)\to h_b(mP){\pi }^{+}{\pi }^{-}$ and ${\rm Y}(5S)\to B^{(\ast )}{\bar{B}}^{(\ast )}\pi$

Abstract

With a combined analysis of data on ${\rm Y}(5S)\to h_b(1P,2P){\pi }^{+}{\pi }^{-}$ and ${\rm Y}(5S)\to B^{(\ast )}{\bar{B}}^{(\ast )}\pi$ in an effective field theory approach, we determine resonance parameters of $Z_b$ states in two scenarios. In one scenario we assume that $Z_b$ states are pure molecular states, while in the other one we assume that $Z_b$ states contain compact components. We find that the present data favor that there should be some compact components inside $Z_b^{(\prime )}$ associated with the molecular components. By fitting the invariant mass spectra of ${\rm Y}(5S)\to h_b(1P,2P){\pi }^{+}{\pi }^{-}$ and ${\rm Y}(5S)\to B^{(\ast )}{\bar{B}}^{\ast }\pi$, we determine that the probability of finding the compact components in $Z_b$ states may be as large as about $40\%$.

Comments: Discussions added, version published in EPJC