Combined analysis of the unitarity triangle and CP violation in the Standard Model

We perform a combined analysis of the unitarity triangle and of the CP violating parameter ε′/ε using the most recent determination of the relevant experimental data and, whenever possible, hadronic matrix elements from lattice QCD. We discuss the rôle of the main non-perturbative parameters and make a comparison with other recent analyses. We use lattice results for the matrix element of Q8 obtained without reference to the strange quark mass. Since a reliable lattice determination of the matrix element of Q6 is still missing, the theoretical predictions for ε′/ε suffer from large uncertainties. By evaluating this matrix element with the vacuum-saturation approximation, we typically find as central value ε′/ε = (4 ÷ 7) × 10−4. We conclude that the experimental data suggest large deviation of the value of the matrix element of Q6 from the vacuum-saturation approximation, possibly due to penguin contractions.