Kaon electromagnetic form factors in dispersion theory

The electromagnetic form factors of charged and neutral kaons are strongly constrained by their low-energy singularities, in the isovector part from two-pion intermediate states and in the isoscalar contribution in terms of omega and phi residues. The former can be predicted using the respective pi pi -> (K) over barK partial-wave amplitude and the pion electromagnetic form factor, while the latter parameters need to be determined from electromagnetic reactions involving kaons. We present a global analysis of time- and spacelike data that implements all of these constraints. The results enable manifold applications: kaon charge radii, elastic contributions to the kaon electromagnetic self energies and corrections to Dashen's theorem, kaon boxes in hadronic light-by-light (HLbL) scattering, and the phi region in hadronic vacuum polarization (HVP). Our main results are: < r(2)>(c) = 0.359(3) fm(2), < r(2)>(n) = -0.060(4) fm(2) for the charged and neutral radii, epsilon = 0.63(40) for the elastic contribution to the violation of Dashen's theorem, a(mu)(K-box) = -0.48(1) x 10(-11) for the charged kaon box in HLbL scattering, and a(mu)(HVP) [K+ K-, <= 1.05 GeV] = 184.5(2.0) x10(-11), a(mu)(HVP) [KSKL, <= 1.05 GeV] = 118.3(1.5) x 10(-11) for the HVP integrals around the phi resonance. The global fit to (K) over barK gives (M) over bar (phi) = 1019.479(5) MeV, (Gamma) over bar (phi) = 4.207(8) MeV for the phi resonance parameters including vacuum-polarization effects.