Review of Exotic Hadrons

TL;DR

This paper reviews recent experimental discoveries of exotic hadrons that challenge traditional quarkonium models, highlighting new states, their quantum numbers, and the emerging spectroscopy of tetraquarks and meson molecules.

Contribution

It provides a comprehensive overview of recent experimental results on exotic hadrons and discusses the development of a new spectroscopy based on these exotic states.

Findings

Multiple new exotic hadron states observed in recent years.

Quantum number determinations support the existence of tetraquarks and meson molecules.

The field is still evolving with ongoing research needed to complete the understanding.

Abstract

I review here the most recent results about the observation and the study of hadronic bound states that do not fit well in the standard quarkonium picture. Several new states have been observed in the last few years, at B-, tau-Factories and hadron colliders. For most of them, quantum number determinations are available and allow to develop the basis of a new spectroscopy based on exotic compounds like tetraquarks or meson molecules. Nonetheless, there is still a lot of work to do to complete the picture.