Lowest vector tetraquark states: $Y(4260/4220)$ or $Z_c(4100)$

TL;DR

This paper uses QCD sum rules to analyze the $Y(4260/4220)$ as a vector tetraquark state, successfully predicting its mass and supporting its classification, while disfavoring the $Z_c(4100)$ as a similar state.

Contribution

First QCD sum rule analysis reproducing the $Y(4260/4220)$ mass as a vector tetraquark state, clarifying its nature.

Findings

Predicted mass $M_Y=4.24 ext{ GeV}$ matches experimental data.

Supports $Y(4260/4220)$ as a vector tetraquark state.

Disfavors $Z_c(4100)$ as a similar tetraquark state.

Abstract

In this article, we take the $Y(4260/4220)$ as the vector tetraquark state with $J^{PC}=1^{--}$, and construct the $C\gamma_5\otimes\stackrel{\leftrightarrow}{\partial}_\mu\otimes \gamma_5C$ type diquark-antidiquark current to study its mass and pole residue with the QCD sum rules in details by taking into account the vacuum condensates up to dimension 10 in a consistent way. The predicted mass $M_{Y}=4.24\pm0.10\,\rm{GeV}$ is in excellent agreement with experimental data and supports assigning the $Y(4260/4220)$ to be the $C\gamma_5\otimes\stackrel{\leftrightarrow}{\partial}_\mu\otimes \gamma_5C$ type vector tetraquark state, and disfavors assigning the $Z_c(4100)$ to be the $C\gamma_5\otimes\stackrel{\leftrightarrow}{\partial}_\mu\otimes \gamma_5C$ type vector tetraquark state. It is the first time that the QCD sum rules have reproduced the mass of the $Y(4260/4220)$ as a vector tetraquark state.