Internal structure of near-threshold states using compositeness

TL;DR

This paper investigates the internal structures of near-threshold states in exotic hadrons using compositeness, revealing that shallow bound states are cluster-dominant while narrow resonances are not, and establishes a theoretical basis for the threshold energy rule.

Contribution

It provides a theoretical framework for understanding the clustering structures of near-threshold states using compositeness, clarifying the nature of shallow bound states and narrow resonances.

Findings

Shallow bound states are typically cluster-dominant.

Near-threshold narrow resonances are generally non-cluster-dominant.

The study establishes a theoretical foundation for the empirical threshold energy rule.

Abstract

Understanding the internal structure of near-threshold states is essential for revealing the nature of exotic hadrons. Motivated by this challenge, we discuss the clustering structures of near-threshold $s$-wave eigenstates using the compositeness, which characterizes the clustering nature of the states. We show that shallow bound states usually possess cluster-dominant structures, while near-threshold narrow resonances are non-cluster-dominant. Through this study, we establish a theoretical foundation for the threshold energy rule, which has been known empirically.