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

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/Nc 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 View the MathML source.