$Z_c(4100)$ and $Z_c(4200)$ as hadrocharmonium

TL;DR

The paper proposes that the $Z_c(4100)$ and $Z_c(4200)$ are hadrocharmonium states related by charm quark spin symmetry, predicting specific decay patterns and production mechanisms that can be experimentally tested.

Contribution

It introduces a hadrocharmonium model linking the $Z_c(4100)$ and $Z_c(4200)$ states via charm quark spin symmetry, providing testable predictions for their properties and production.

Findings

$Z_c(4100)$ is mainly $ ext{η}_c$ embedded in light-quark excitation.

$Z_c(4200)$ contains $J/ ext{ψ}$ instead of $ ext{η}_c$.

Predicted decay relations and production in $ar{p}p$ annihilation.

Abstract

It is suggested that the recently reported charged charmoniumlike resonance $Z_c(4100)$ and the previously observed $Z_c(4200)$ are two states of hadrocharmonium, related by the charm quark spin symmetry in the same way as the lowest charmonium states $\eta_c$ and $J/\psi$. Namely, the $Z_c(4100)$ is (dominantly) the $\eta_c$ embedded in an light-quark excitation with quantum numbers of a pion, while the $Z_c(4200)$ is a similar four quark state containing $J/\psi$ instead of $\eta_c$. It is argued that this picture suggests certain relations between the properties of the two exotic resonances and a distinctive pattern of their decays that can be tested experimentally. It is also pointed out that due to the presence of a spatially compact $c \bar c$ charmonium the discussed exotic $Z_c$ states may be produced as resonances in the $s$ channel in $\bar p p$ annihilation.