Pion form factor from a contact interaction

TL;DR

This paper investigates the pion form factor using a momentum-independent contact interaction within a Poincare'-covariant framework, revealing limitations in describing experimental data and asymptotic behavior.

Contribution

It introduces a symmetry-preserving regularization of a contact interaction to study pion properties, highlighting discrepancies with experimental and perturbative-QCD results.

Findings

Contact interaction describes static pion properties.

Form factor evolution disagrees with experimental data beyond 0.17 GeV^2.

Asymptotic behavior conflicts with perturbative-QCD predictions.

Abstract

In a Poincare'-covariant vector-boson-exchange theory, the pion possesses components of pseudovector origin, which materially influence its observable properties. For a range of such quantities, we explore the consequences of a momentum-independent interaction, regularised in a symmetry-preserving manner. The contact interaction, whilst capable of describing pion static properties, produces a form factor whose: evolution for Q^2>0.17GeV^2 disagrees markedly with experiment; and asymptotic power-law behaviour conflicts strongly with perturbative-QCD.