Timelike Form Factor of the Kaon for |Q^2|=M^2(J/psi)

TL;DR

This paper calculates the timelike form factor of the charged kaon at a specific energy scale using J/psi decay data, and finds it consistent with recent direct measurements at a higher energy.

Contribution

It provides a novel evaluation of the kaon form factor at |Q^2|=9.59 GeV^2 using J/psi decay branching ratios, connecting it to experimental data.

Findings

The form factor value at 9.59 GeV^2 is 0.81+-0.18 GeV^2.

The evaluated form factor agrees with the direct measurement at 13.5 GeV^2.

The method relates decay branching ratios to the kaon form factor.

Abstract

The timelike form factor of the charged kaon is evaluated at |Q^2|=M^2(J/psi)=9.59 GeV^2 by relating it to B(J/psi->K+K-), B(J/psi->K_SK_L) and B(J/psi->e+e-). The resulting value, |Q^2|F_K(9.59 GeV^2)=0.81+-0.18 GeV^2 is found to be in good agreement with |Q^2|F_K(13.5 GeV^2)=0.85+-0.05 GeV^2 obtained recently by the direct measurement of the reaction e+e--> K+K-.