Structure Effects in the DecaysKL,S→γ+DalitzPair

We investigate the form factors associated with the vertices $K_{1,2}\to \gamma \gamma$ when one of the photons is virtual and their influence on the rate and spectrum of the Dalitz pair reactions $K_{1,2}\to \gamma l^{+}{l}^{-}$. We find that while the form factor in $K_2\to \gamma \gamma$ produces a small uniform enhancement, that in $K_1\to \gamma \gamma$ suppresses the relative probability of lepton pairs of large invariant mass ($\sqrt{t}$), an effect that should be most noticeable in the decay $K_1\to \gamma {\mu }^{+}{\mu }^{-}$ for muon pairs of $t>\mathrm{}4\mathrm{}{\left(\mathrm{pion}\mathrm{mass}\right)}^2$.