$Z_c(3900)$ as a Four-Quark State

TL;DR

This paper uses QCD Sum Rules to analyze the $Z_c(3900)$ particle, suggesting it is a tetra-quark state with a mass around 3.9 GeV, contributing to understanding exotic hadrons.

Contribution

It applies QCD Sum Rules to identify the $Z_c(3900)$ as a four-quark state, providing a theoretical mass estimate consistent with experimental observations.

Findings

Mass estimate of $Z_c(3900)$ around 3.9 GeV

Supports the tetra-quark interpretation of $Z_c(3900)$

Demonstrates the effectiveness of QCD Sum Rules in exotic hadron analysis

Abstract

Using the method of QCD Sum Rules, we derive the correlator $\Pi^Z$ for a state consisting of two charm quarks and two light quarks, $c\bar{c}u\bar{d}$, and carry out a Borel transform to find $\Pi^Z(M_B)$. From this we find the solution that $M_B\simeq 3.9 \pm .2$ GeV, showing that the $Zc(3900)$ is a tetra-quark state.