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Publications
Saturation of counterterms by resonances inK →πe + e − decays

# Saturation of counterterms by resonances inK →πe + e − decays,10.1007/BF02906988,European Physical Journal C,S. Fajfer,J. Stefan

Saturation of counterterms by resonances inK →πe + e − decays
The decays $K^{+} \rightarrow \pi^{+} e^{+} e^{-}$, $K_{S} \rightarrow \pi^{0} e^{+} e^{-}$ and $K_{L} \rightarrow \pi^{0} e^{+} e^{-}$ are reinvestigated within the framework of chiral perturbation theory. The counterterms induced by strong, electromagnetic and weak interactions are determined assuming the resonance exchange. The weak deformation model, the factorization model and the large $N_{c}$ limit are used to create a weak Lagrangian. It is found that the results of the first two approaches depend on the $H_{1}$ coupling, defined in the effective chiral Lagrangian of the ${\it O} (p^{4})$ order. The set of parameters used in the extended Nambu and Jona-Lasinio model can accommodete $K^{+} \rightarrow \pi^{+} e^{+} e^{-}$ decay rate within the factorization approach. The CP violating $K_{L} \rightarrow \pi^{0} e^{+} e^{-}$ decay rate is discussed.