QCD studies and discoveries with e+e- colliders and future perspectives

TL;DR

This paper reviews recent discoveries of new quarkonium-like states at e+e- colliders, discusses the limitations of traditional potential models, and explores how future experiments can shed light on their nature.

Contribution

It highlights the failure of conventional potential models to explain new states and emphasizes the role of symmetries and future collider experiments in understanding these exotic particles.

Findings

New charmonium-like and bottomonium-like states observed at e+e- colliders.

Traditional potential models fail to describe many of these new states.

Future experiments like Panda and Belle II are crucial for understanding their nature.

Abstract

Observations of new charmonium(-like) and bottomonium(-like) states (sometimes refered to as "XYZ" states) at e+e- colliders have changed our picture of quarkonia systems as QCD bound states. Potential models with a linear confinement ansatz, which were able to predict many conventional states with an accuracy of ~1 MeV, absolutely fail in describing many of the new states. Symmetries play an important role e.g. in the determination of the quantum numbers (such as charge conjugation in the radiative decays) or in trying to explain surprising properties such as isospin violation. It will also be discussed, how future experiments (Panda, Belle II) can help to understand the nature of these states.