No serious meson spectroscopy without scattering

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.