Lattice B-parameters for ΔS=2 and ΔI=3/2 operators

We compute several matrix elements of dimension-six four-fermion operators and extract their B-parameters. The calculations have been performed with the tree-level Clover action at β=6.0. The renormalization constants and mixing coefficients of the lattice operators have been obtained non-perturbatively. In the MS renormalization scheme, at a renormalization scale μ≃2 GeV, we find BK (B93/2)=0.66(11), B73/2=0.72(5) and B83/2=1.03(3). The result for B83/2 has important implications for the calculation of ϵ′/ϵ.