The $X(4140)$, $X(4274)$, $X(4500)$ and $X(4700)$ in the relativized quark model

TL;DR

This paper uses a relativized quark model to analyze the masses of $cs ar c ar s$ tetraquark states, explaining several observed resonances and proposing assignments for their internal structures.

Contribution

It introduces a detailed relativized quark model approach to identify the nature of specific charmonium-like states as tetraquarks or conventional mesons.

Findings

X(4140) is a ground state tetraquark.

X(4700) is a 2S excited tetraquark.

X(4500) is a tetraquark with a 2S scalar diquark.

Abstract

We investigate the masses of $cs \bar c \bar s$ tetraquark states in a diquark-antidiquark picture employing the relativized quark model proposed by Godfrey and Isgur. Only the antitriplet diquark states in color space are calculated. The diquark masses are obtained with the relativized potential firstly, and then the diquark and antidiquark are treated as the usual antiquark and quark, respectively, and the masses of the tetraquark states are obtained by solving the Schr\"{o}dinger equation with the relativized potential between the diquark and antidiquark. The theoretical uncertainties induced by screening effects are also taken into account. It is found that the resonance of $X(4140)$ can be regarded as the $cs \bar c \bar s$ tetraquark ground states, and the $X(4700)$ can be assigned as the $2S$ excited tetraquark state. When the internal excited diquarks are taken into account, the resonance of $X(4500)$ can be explained as the tetraquark composed of one $2S$ scalar diquark and one scalar antidiquark. In our approach, the $X(4274)$ cannot be explained as a tetraquark state, however, it can be a good candidate of the conventional $\chi_{c1}(3^3P_1)$ state. In addition, other charmonium-like states $\chi_{c0}(3915)$, $X(4350)$, $X(4630)$ and $X(4660)$, as the $cs \bar c \bar s$ tetraquark states, are also discussed.