Is $Z_b(10610)$ a Molecular State?

Abstract

Whether molecular states indeed exist in nature has been disputed for a long time. Several new resonances have been observed in the recent experiments and they seem to be of exotic structures and some of them have been proposed to be molecular states. The very recent observation of $Z_b(10610)[(10608.4\pm 2.0)$ MeV] and $Z_b(10650)[(10653.2\pm 1.5)$ MeV] encourages the interpretation of multi-quark states. In the Beter-Salpeter (BS) approach, we study the possibility if two heavy mesons can form a molecular state by exchanging light mesons. Our results indicate that two heavy mesons can form an isospin singlet (I=0) bound state but cannot form an isospin triplet (I=1) when the contribution of $\sigma -$ exchange is reasonably small, i.e. as the coupling of $\sigma$ with mesons $g_{\sigma }$ takes the value given in previous literatures. Thus we conclude that the newly observed $Z_b(10610)$ should not be a molecular state, but a tetraquark state instead, at most, the fraction of the molecular state in the physical resonance $Z_b(10610)$ is tiny.

15 pages, 2 figures, an important reference added; Accepted by JHEP

References in corpus (5)

• Observation of a resonance-like structure in the pi^+- psi' mass distribution in exclusive B-->K pi^+- psi' decays
• Possible S-wave Bound-States of Two Pseudoscalar Mesons
• The Scalar Meson f0(980) in Heavy-Meson Decays
• Studying the scalar bound states of the $K\bar{K}$ system in the Bethe-Salpeter formalism
• $B^{(\ast )}{\bar{B}}^{(\ast )}$ intermediate state contribution to ${\rm Y}(4S,5S)\to {\eta }_b+\gamma$ radiative decay

Cited by in corpus (7)

• Confirming the molecular nature of the $Z_b(10610)$ and the $Z_b(10650)$
• Study of the $B{\bar{B}}^{\ast }/D{\bar{D}}^{\ast }$ bound states in a Bethe-Salpeter approach
• Study of $B{\bar{B}}^{\ast }$ and $B^{\ast }{\bar{B}}^{\ast }$ interactions in $I=1$ and relationship to the $Z_b(10610)$, $Z_b(10650)$ states
• More hidden heavy quarkonium molecules and their discovery decay modes
• Analysis of the hidden-bottom tetraquark mass spectrum with the QCD sum rules
• Spectroscopic parameters and decays of the resonance $Z_b(10610)$
• Insights into $Z_b(10610)$ and $Z_b(10650)$ from dipion transitions from ${\rm Y}(10860)$