No serious meson spectroscopy without scattering

TL;DR

Understanding meson spectra requires accounting for dynamical quark effects, as neglecting them in models leads to significant inaccuracies, which lattice QCD calculations now confirm.

Contribution

This paper emphasizes the importance of including quark-pair creation and decay effects in meson spectroscopy, challenging traditional quark models that ignore these dynamical effects.

Findings

Quenched lattice calculations show discrepancies of hundreds of MeV in meson spectra.

Models with redefined quark masses or screening cannot replicate non-perturbative effects.

Neglecting dynamical effects distorts the understanding of meson confinement.

Abstract

The principal purpose of meson spectroscopy is to understand the confining force, which is generally assumed to be based on low-energy QCD. This is usually done in the context of quark models that ignore the dynamical effects of quark-pair creation and decay. Very recent lattice calculations confirm much earlier model results showing that neglecting such effects, in the so-called quenched approximation, may give rise to discrepancies of hundreds of MeV, and so distort the meson spectra resulting from quark confinement only. Models attempting to mimic unquenching through a redefinition of the constituent quark mass or screening of the confining potential at larger interquark separations are clearly incapable of accounting for the highly non-perturbative and non-linear effects on mesonic bound-state and resonance poles, as demonstrated with several published examples.