Hadronic structure on the light-front VIII. Light scalar and vector mesons

TL;DR

This paper investigates the structure of light scalar and vector mesons using the QCD instanton vacuum model, deriving their distribution amplitudes, PDFs, and form factors, and comparing results with empirical data.

Contribution

It introduces a detailed light-front analysis of mesons within the instanton vacuum framework, including molecular interactions and explicit derivation of distribution amplitudes and form factors.

Findings

Vector mesons can be bound by molecular interactions despite suppression.

Derived distribution amplitudes and PDFs agree with empirical and lattice data after QCD evolution.

Electric form factors for pion and rho match current experimental measurements.

Abstract

We use the QCD instanton vacuum model to discuss the emergence of the light scalar and vector mesons on the light front. We take into account both the instanton and anti-instanton single and molecular interactions on the light quarks, in the form of non-local effective interactions. Although the molecular induced interactions are suppressed by a power of the packing fraction, they are still sufficient to bind the vector mesons, while keeping most of the scalar spectrum relatively unchanged. We explicitly derive the light front distribution amplitudes (DAs) and partonic functions (PDFs) for the scalar and vector mesons, and compare them after pertinent QCD evolution, to the available empirical and lattice measured counterparts. The Dirac electric form factors for both the pion and rho meson are derived, and shown to compare well with current data.