K -> 3 Pi Decays in Chiral Perturbation Theory

A kaon decaying into three pions is an example of a weak process. However, since the quarks are confined into mesons, the strong interaction also plays an important part. The reaction is a low-energy one, meaning that it takes place in the non-perturbative region of QCD. In that region perturbative QCD doesn't give you any answers and other methods have to be used. The one we use is called Chiral Perturbation Theory.