Towards a theory of hadron resonances

TL;DR

This review discusses current methods like lattice QCD and effective field theories for understanding the hadron resonance spectrum, highlighting synergies and limitations of common parameterizations.

Contribution

It provides a systematic, model-independent overview of calculating the hadron spectrum and critiques the Breit-Wigner parameterization in strongly coupled channels.

Findings

Synergies between lattice QCD and effective field theories enhance understanding.

Breit-Wigner parameterization is inadequate for strongly coupled channels.

Results demonstrate the importance of chiral symmetry considerations.

Abstract

In this review, we present the current state of the art of our understanding of the spectrum of excited strongly interacting particles and discuss methods that allow for a systematic and model-independent calculation of the hadron spectrum. These are lattice QCD and effective field theories. Synergies between both approaches can be exploited allowing for deeper understanding of the hadron spectrum. Results based on effective field theories and hadron-hadron scattering in lattice QCD or combinations thereof are presented and discussed. We also show that the often used Breit-Wigner parameterization is at odds with chiral symmetry and should not be used in case of strongly coupled channels.