ΔS=1,2 effective weak chiral Lagrangian from the instanton vacuum

Abstract

We study the effective weak chiral Lagrangian from the instanton vacuum. We incorporate the effective weak Hamiltonian into the effective low-energy partition function defining the chiral symmetric quark–Goldstone-boson interactions with the momentum-dependent dynamical quark mass. Employing the derivative expansion and the 1/ N c expansion, we derive the corresponding bosonic weak effective Lagrangian in leading order with the low-energy constants to be used, e.g., in chiral perturbation theory. We find that the momentum-dependent dynamical quark mass plays an essential role in improving the low-energy constants and their ratio g 8 /g 27 .