Spin - 1 resonance contributions to the weak Chiral Lagrangian : the vector field formulation ∗

We use the Vector formulation to evaluate vector and axial–vector exchange contributions to the O(p4) weak Chiral Lagrangian. We recover in this framework the bulk of the contributions found previously by Ecker et al. in the antisymmetric formulation of vectors and axial–vectors, but new interesting features arise : i) most of our results are independent of Factorization and ii) novel contributions to non-leptonic kaon decays, proper of this formulation and phenomenologically interesting, are found. The phenomenological implications for K → ππ(π) and radiative (anomalous and non-anomalous) non–leptonic kaon decays are thus investigated and found particularly relevant. PACS : 12.15.-y,12.39.Fe,12.40.Vv,13.25.Es