Scalar mesons: fifty years of challenging the quark model

TL;DR

This paper reviews fifty years of research on light scalar mesons, discussing various theoretical models and recent lattice-QCD results to understand their nature and challenge the traditional quark model.

Contribution

It provides a comprehensive overview of different theoretical and phenomenological approaches to light scalar mesons, including recent lattice-QCD simulations, highlighting ongoing challenges.

Findings

Multiple models describe scalar mesons with varying success

Recent lattice-QCD offers new insights into meson structure

The nature of light scalar mesons remains an open question

Abstract

Half a century of work on the light scalar mesons $f_0(500)$, $f_0(980)$, $K_0^\star(700)$, and $a_0(980)$ is briefly reviewed. After summarising all light scalar candidates in the Review of Particle Physics since 1963, a selection of different theoretical and phenomenological descriptions is presented, including pure meson-meson models, a tetraquark construction, unitarised quark-meson models, unitarised effective chiral approaches, and a very recent lattice-QCD simulation.