Vector-meson production and vector meson dominance

TL;DR

This paper critically examines the validity of the vector meson dominance (VMD) model in relating electromagnetic and hadronic processes, finding it reliable for light mesons but failing for heavy mesons due to momentum-dependent effects.

Contribution

The study highlights the limitations of VMD for heavy vector mesons, emphasizing the need to reassess related cross-section estimates and theoretical conclusions.

Findings

VMD is reasonable for light vector mesons based on photon vacuum polarisation analysis.

VMD fails for heavy vector mesons when using momentum-dependent bound-state amplitudes.

Reliance on VMD for heavy mesons can lead to inaccurate estimates of transition strengths.

Abstract

We consider the fidelity of the vector meson dominance (VMD) assumption as an instrument for relating the electromagnetic vector-meson production reaction $e + p \to e^\prime + V + p$ to the purely hadronic process $V + p \to V+p$. Analyses of the photon vacuum polarisation and the photon-quark vertex reveal that such a VMD Ansatz might be reasonable for light vector-mesons. However, when the vector-mesons are described by momentum-dependent bound-state amplitudes, VMD fails for heavy vector-mesons: it cannot be used reliably to estimate either a photon-to-vector-meson transition strength or the momentum dependence of those integrands that would arise in calculations of the different reaction amplitudes. Consequently, for processes involving heavy mesons, the veracity of both cross-section estimates and conclusions based on the VMD assumption should be reviewed, e.g., those relating to hidden-charm pentaquark production and the origin of the proton mass.