Study of the Zc+ channel in lattice QCD

TL;DR

This lattice QCD study investigates the $Z_c$ channel to understand the nature of charged charmonium-like states, but finds no evidence of a $Z_c$ resonance in the simulated energy region.

Contribution

The paper performs a comprehensive lattice QCD simulation including various two-meson and diquark operators to search for the $Z_c$ state, providing new insights into its non-observation.

Findings

All relevant two-meson levels identified within the energy region.

No additional level consistent with $Z_c$ observed.

Results suggest $Z_c$ may not be a simple two-meson resonance.

Abstract

Several charged charmonium-like hadrons called $Z_c$ have been recently discovered by different experiments. In contrast to conventional hadrons these contain at least two valence quarks and antiquarks ($\bar{c}c\bar{d}u$). We perform a lattice QCD simulation of the $I^G(J^{PC})=1^+(1^{+-})$ channel including all relevant two-meson operators under 4.3 GeV: $J/\psi \pi$, $\psi_{2S}\pi$, $\psi_{1D}\pi$, $D \bar{D}^*$, $D^* \bar{D}^*$, $\eta_c \rho$ as well as additional diquark anti-diquark operators. In our $N_f = 2$ simulation with pion mass at 266 MeV we are able to identify all two-meson levels within the energy region of interest. However we find no additional level identifiable as a candidate for $Z_c$.