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-viol ating parameter epsilon'/epsilon using tho most recent determination of the relevant experimental data and, whenever possible, hadronic matrix element s from lattice QCD. We discuss the role of the main non-per turbative param eters and make a comparison with other recent analyses. We use lattice resu lts for the matrix clement of Q(8) obtained without reference to the strang e quark mass. Since a reliable lattice determination or the matrix element of Q(6) is still missing, the theoretical predictions for epsilon'/epsilon suffer from large uncertainties. By evaluating this matrix clement with the vacuum-saturation approximation, we typically find as central value epsilo n'/epsilon = (4-7) X 10(-4). We conclude that the experimental data suggest large deviation of the value of the matrix element of Q(6) from the vacuum -saturation approximation, possibly due to penguin contractions. (C) 2000 E lsevier Science B.V. All rights reserved.