📝 SummarXiv

Abstract

We provide a modern pedagogical introduction to light mesons. We discuss their masses and widths, their classification into multiplets of isospin and flavor SU(3), as well as other quantum numbers, mixing schemes, observable states, and their disposition in Regge trajectories. We briefly introduce the relevant concepts of Quantum Chromodynamics, including confinement, chiral symmetry, and the relationship between poles and resonances. We discuss their interpretation in terms of quark-model ordinary quark-antiquark states or non-ordinary states like exotics, multiquarks, or glueballs. Finally, we comment on the open issues that are still under discussion.