Weakly-induced strong CP violation

Weak interaction contributions to the strong θ parameter are revisited in the frame of a large-Nc Chiral Perturbation Theory. Focusing on the hadronic η(′)→ππ amplitudes, we express these second-order corrections in terms of the CP-violating parameter in K→ππ decays to obtain Δwθ≈10−17 at O(GF2ε′).