https://doi.org/10.1140/epjc/s10052-022-10348-3
Regular Article - Theoretical Physics
Kaon electromagnetic form factors in dispersion theory
1
Helmholtz-Institut für Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Universität Bonn, 53115, Bonn, Germany
2
Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland
3
Physik-Institut, Universität Zürich, Winterthurerstrasse 190, 8057, Zürich, Switzerland
4
Paul Scherrer Institut, 5232, Villigen PSI, Switzerland
Received:
24
February
2022
Accepted:
17
April
2022
Published online:
11
May
2022
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 
and 
residues. The former can be predicted using the respective 
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 region in hadronic vacuum polarization (HVP). Our main results are: 
, 
for the charged and neutral radii, 
for the elastic contribution to the violation of Dashen’s theorem, 
for the charged kaon box in HLbL scattering, and 
, 
for the HVP integrals around the resonance. The global fit to 
gives 
, 
for the resonance parameters including vacuum-polarization effects.
© The Author(s) 2022
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Funded by SCOAP3
