Lattice QCD confronts the unitarity triangle fit.

Before the starting of the B factories, the Unitarity Triangle (UT) analysis relied on the results of lattice QCD simulations to relate the experimental determinations of semileptonic B decays, K0 - over(K, -)0 and Bd, s 0 - over(B, -)d, s 0 mixing to the CKM parameters. In the last years, much more information has been obtained from the direct determination of the UT angles from non-leptonic B decays. In this talk, we compare the results of the "classical" UT analysis (UTlattice) with the analysis based on the angles determinations (UTangles). We show that the recent measurement of Δ ms, combined with Δ md and εK, allows from this comparison a quite accurate extraction of the values of the lattice parameters, over(B, ̂)K, fB s over(B, ̂)B s 1 / 2, ξ and fB. These values, obtained "experimentally" by assuming the validity of the Standard Model, can be compared with the theoretical predictions from lattice QCD. We also discuss the different determinations of Vu b and show that current data do not favor the value measured in inclusive decays. Finally, we present updated predictions for the leptonic branching fraction B R (B → τ ντ), and compare them with the recent experimental determination. We take the opportunity of this write up to update the results of ref. [M. Bona et al. [UTfit Collaboration], arXiv:hep-ph/0606167] with the most recent results presented at the ICHEP'06 conference. © 2006 Elsevier B.V. All rights reserved.