The B-K kaon parameter in the chiral limit

We introduce four-point functions in the hadronic ladder resummation approach to large N-c QCD Green functions. We determine the relevant one to calculate the B-K kaon parameter in the chiral limit. This four-point function contains both the large momenta QCD OPE and the small momenta ChPT at NLO limits, analytically. We get (B) over cap (X)(K) = 0.38 +/- 0.15. We also give the ChPT result at NLO for the relevant four-point function to calculate B-K outside the chiral limit, while the leading QCD OPE is the same as the chiral limit one