Deciphering the charged heavy quarkoniumlike states in chiral effective field theory

TL;DR

This paper extends chiral effective field theory to analyze charged heavy quarkoniumlike states, fitting experimental data to identify these states as molecular resonances rather than bound states, and explores their heavy quark symmetry relations.

Contribution

It introduces a next-to-leading order chiral EFT framework for heavy meson interactions, incorporating various force contributions and wave mixing, to interpret experimental resonance data.

Findings

Charged charmoniumlike and bottomoniumlike states are identified as molecular resonances.

Bound state explanations are ruled out within this framework.

Heavy quark symmetry relates the $Z_c$ and $Z_b$ states as twin partners.

Abstract

We generalize the framework of chiral effective field theory to study the interactions of the isovector $D^\ast\bar{D}^{(\ast)}$ and $B^\ast\bar{B}^{(\ast)}$ systems up to the next-to-leading order, in which the long-, mid-, and short-range force contributions as well as the $S$-$D$ wave mixing are incorporated. Based on the Lippmann-Schwinger equation, we fit the invariant mass distributions of the elastic channels measured by the BESIII and Belle Collaborations. Our results indicate that the four charged charmoniumlike and bottomoniumlike states $Z_c(3900)$, $Z_c(4020)$ and $Z_b(10610)$, $Z_b(10650)$ can be well identified as the $D\bar{D}^{\ast},D^\ast\bar{D}^{\ast}$ and $B\bar{B}^{\ast},B^\ast\bar{B}^{\ast}$ molecular resonances. The bound state explanations are vetoed in our framework. Our study favors the $Z_c$ and $Z_b$ states are the twin partners under the heavy quark symmetry.