Operators without Quark Masses

We introduce a new parameterization of four-fermion operator matrix elements which does not involve quark masses and thus allows a reduction of systematic uncertainties. In order to simplify the matching between lattice and continuum renormalization schemes, we express our results in terms of renormalization group invariant B-parameters which are renormalization-scheme and scale independent. As an application of our proposal, matrix elements of ∆I = 3/2 and SUSY ∆S = 2 operators have been computed. The calculations have been performed using the tree-level improved Clover lattice action at two different values of the strong coupling constant (β = 6/g2 = 6.0 and 6.2), in the quenched approximation. Renormalization constants and mixing coefficients of lattice operators have been obtained non-perturbatively. Using lowest order χPT, we also obtain 〈ππ|O7|K〉 I=2 = (0.11 ± 0.02) GeV4 and 〈ππ|O8|K〉 I=2 = (0.51 ± 0.05) GeV4 at μ = 2 GeV. PACS: 11.15.H, 12.38.G, 14.40.Aq and 12.15.Hh Preprint submitted to Elsevier Preprint 1 February 2008