K0 and K+ meson electromagnetic form factors: a nonperturbative relativistic quark model versus experimental, perturbative and lattice Quantum-Chromodynamics results

TL;DR

This paper uses a nonperturbative relativistic quark model to accurately describe the electromagnetic form factors of K mesons, aligning with experimental, lattice, and QCD asymptotic results across different energy scales.

Contribution

It extends a successful quark model approach from pi to K mesons, providing precise charge radius constraints and matching various experimental and theoretical results.

Findings

Accurate K0 charge radius measurement constrains model parameters.

Model matches experimental data, lattice results, and QCD asymptotics for K+ form factor.

Extended the infrared-ultraviolet connection from pi to K mesons.

Abstract

It has been previously shown that a particular nonperturbative constituent-quark model of hadrons describes experimental measurements of electromagnetic form factors of light charged mesons through a small number of common phenomenological parameters, matching at the same time the Quantum-Chromodynamics (QCD) asymptotics for the pi-meson form factor at large momentum transfer. Here we start with the determination of the K0 electromagnetic form factor in this approach. Precise measurement of the K0 charge radius makes it possible to constrain model parameters with high accuracy. Then, with all parameters fixed, we revisit the K+ form factor and find that it matches experimental measurements in the infrared, lattice results at moderate momentum transfer and the perturbative QCD asymptotics in the ultraviolet. In this way we obtain a narrow constraint on the K+ charge radius, <r_K+^2> = 0.403 +0.007 -0.006 fm^2, and extend the successful infrared-ultraviolet connection from pi to K mesons.