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

Abstract

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