# Evidence for $Z_{c}^{\pm}$ decays into the $\rho^{\pm} \eta_{c}$ final state

## TL;DR

This study reports evidence for the decay of the exotic $Z_c^{\u00b1}$ states into $
ho^{b1}\u03b5_c$, measuring the cross section at specific energies and setting upper limits at others, aiding understanding of their nature.

## Contribution

First evidence of $Z_c^{b1} o
ho^{b1}\u03b5_c$ decay, with measured cross section and ratios to other decay modes, providing new insights into the structure of these exotic states.

## Key findings

- Evidence for $Z_c^{b1} o
ho^{b1}\u03b5_c$ at 4.226 GeV with 3.9$\sigma$ significance.
- Measured cross section times branching fraction: $(48 \u00b1 11 \u00b1 11)$ pb.
- Upper limits set at other energies; ratios of decay modes used to test theoretical models.

## Abstract

We study $e^{+}e^{-}$ collisions with a $\pi^{+}\pi^{-}\pi^{0}\eta_{c}$ final state using data samples collected with the BESIII detector at center-of-mass energies $\sqrt{s}=4.226$, $4.258$, $4.358$, $4.416$, and $4.600$ GeV. Evidence for the decay $\zcpm\to\rhopm\etac$ is reported with a statistical significance of $3.9\sigma$ with various systematic uncertainties taken into account at $\sqrt{s} = 4.226$ GeV, and the Born cross section times branching fraction $\sigma^{B}(\EE\to \pimp\zcpm)\times \BR(\zcpm\to\rhopm\etac)$ is measured to be $(48 \pm 11 \pm 11)\,\rm{pb}$. The $\zcpm\to \rhopm\etac$ signal is not significant at the other center-of-mass energies and the corresponding upper limits are determined. In addition, no significant signal is observed in a search for $\zcppm\to \rho^{\pm}\etac$ with the same data samples. The ratios $R_{\zc}=\BR(\zcpm\to \rho^{\pm} \etac)/\BR(\zcpm\to \pi^{\pm} \jpsi)$ and $R_{\zcp}=\BR(\zcppm\to \rho^{\pm} \etac)/\BR(\zcppm\to \pi^{\pm} \hc)$ are obtained and used to discriminate between different theoretical interpretations of the $\zcpm$ and $\zcppm$.