Exotic candidates with heavy quark(s)

TL;DR

This paper reviews the rapid growth of exotic hadron candidates beyond the traditional quark model, discussing various theoretical interpretations and emphasizing the distinguishing features of hadronic molecules, exemplified by the Z_b states.

Contribution

It provides an overview of exotic heavy quark candidates, compares different models, and highlights the molecular interpretation with specific case studies.

Findings

Identification of features distinguishing hadronic molecules from other configurations

Analysis of the two Z_b states as examples of molecular states

Discussion of the mixing of different configurations with the same quantum numbers

Abstract

In the last decades, the number of exotic candidates which are beyond the conventional quark model has grown dramatically. At the same time, numerous theoretical interpretations, such as tetraquark, hybrid, hadroquarkonium and hadronic molecule, have been proposed to understand their nature. In principle, all the configurations with the same quantum numbers can mix with each other. Thus at present we aim at identifying the prominent component. As an extended object, a hadronic molecule has some distinguishable features from other more compact configurations. In the end, the two $Z_b$ states are used to illustrate some features of the molecular scenario.