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

The decaysK+→π+e+e−,KS→π0e+e− andKL→π0e+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 largeNc limit are used to create a weak Lagrangian. It is found that the results of the first two approaches depend on theH1 coupling, defined in the effective chiral Lagrangian of theO(p4) order. The set of parameters used in the extended Nambu and Jona-Lasinio model can accommodeteK+→π+e+e− decay rate within the factorization approach. The CP violatingKL→π0e+e− decay rate is discussed.