revised On SU(2) Chiral Perturbation Theory for K → ππ Decay Amplitudes

We study the CP conserving decays K → pipi using SU(2)L × SU(2)R Chiral Perturbation Theory (SU(2) ChPT) at next-to-leading order. The external pions in K → pipi are hard, thus complicating the power counting of the theory. However we provide arguments about the possibility of calculating the pion chiral logarithms, i.e. the corrections of O(M2log(M2)), for the nonleptonic decay K → pipi. A compariso