Lattice calculations of matrix elements relevant for kaon decays, and in particular for ε/ε, are reviewed. The rôle of the strange quark mass is also discussed. A comparison with other non-perturbative approaches used to compute kaon decay amplitudes is made. † Presented by G. Martinelli.

The present theoretical status of the parameter for direct CP violation ε/ε in the Standard Model is reviewed and compared with most recent experimental measurements of the same quantity. After collecting the basic expressions for ε/ε, the situation of hadronic matrix element calculations is summarised. The matrix elements constitute the dominant source of uncertainty for theoretical determinat...

I shortly review the present status of the theoretical calculations of ε/ε and the comparison with the present experimental results. I discuss the role of higher order chiral corrections and in general of non-factorizable contributions for the explanation of the ∆I = 1/2 selection rule and direct CP violation in kaon decays. Still lacking satisfactory lattice calculations, analytic methods and ...

We review the present theoretical status of the CP violating ratio ε/ε in the Standard Model (SM) and confront its estimates with the most recent data. In particular we review the present status of the most important parameters ms, B (1/2) 6 , B (3/2) 8 , Λ (4) MS and Ωη+η′ . While the sign and the order of magnitude of SM estimates for ε/ε agree with the data, for central values of these param...

We review the theory of ε/ε and present an updated phenomenological analysis using hadronic matrix elements from lattice QCD. The present status of the computation of ε/ε, considering various approaches to the matrix-element evaluation, is critically discussed. ⋆ based on the talks given by M.C. at “Les Rencontres de Physique de la Vallée d’Aoste”, La Thuile (Italy), 27 February–4 March 2000 an...

The long-distance contributions to K → 2π amplitudes can be pinned down, using well established Chiral Perturbation Theory techniques. The strong S–wave rescattering of the two final pions generates sizeable chiral loop corrections, which have an important impact on the direct CP violation ratio ε/ε [1,2]. Including all large logarithmic corrections, both at short and long distances, the Standa...