Are there compact heavy four-quark bound states?

TL;DR

This paper introduces an exact hyperspherical harmonics method to investigate the potential existence of compact four-quark bound states, especially those containing heavy and light quarks, providing new insights into their stability.

Contribution

It develops a precise computational approach to analyze four-quark systems and delineates the conditions under which compact bound states may exist, highlighting differences between various quark configurations.

Findings

$QQ\bar n \bar n$ states may be stable

Stability of $Q\bar Qn \bar n$ states suggests complex quark correlations

Boundaries for existence of compact four-quark states established

Abstract

We present an exact method to study four-quark systems based on the hyperspherical harmonics formalism. We apply it to several physical systems of interest containing two heavy and two light quarks using different quark-quark potentials. Our conclusions mark the boundaries for the possible existence of compact, non-molecular, four-quark bound states. While $QQ\bar n \bar n$ states may be stable in nature, the stability of $Q\bar Qn \bar n$ states would imply the existence of quark correlations not taken into account by simple quark dynamical models