The K-meson form factor and charge radius: linking low-energy data to future high-energy Jefferson Laboratory results

TL;DR

This paper models the K-meson electromagnetic form factor based on a pi-meson model, fits it to existing data to estimate the charge radius, and discusses how future experiments will refine these measurements.

Contribution

It extends a pi-meson form factor model to the K-meson, linking low-energy data to future high-energy measurements for improved charge radius determination.

Findings

Preferred charge radius range close to lattice results

Current data yields poor accuracy in r_K

Future Jefferson Laboratory measurements will improve precision

Abstract

Starting from a successful model of the pi-meson electromagnetic form factor, we calculate the similar form factor, f_K(Q^2), of the charged K meson for a wide range of the momentum transfer squared, Q^2. The only remaining free parameter is to be determined from the measurements of the K-meson charge radius, r_K. We fit this single parameter to the published data of the NA-7 experiment which measured f_K(Q^2) at Q^2->0 and determine our preferred range of r_K, which happens to be close to recent lattice results. Still, the accuracy in the determination of r_K is poor. However, future measurements of the K-meson electromagnetic form factor at Q^2<~5.5 GeV^2, scheduled in Jefferson Laboratory for 2017, will test our approach and will reduce the uncertainty in r_K significantly.