CKM matrix: the `over-consistent' picture of the unitarity triangle

Abstract

In presenting an up-to-date account of the experimental knowledge of the CKM matrix, special emphasis is placed on the exceptional degree of consistency shown by the current Standard Model determination of the unitarity triangle; some implications in the question of how the theoretical nature of the dominant uncertainties affects the Standard Model predictions are discussed. Recent experimental results include improved determinations of |V_{cb}| by OPAL and CLEO, the confirmation of rare (charmless hadronic and electromagnetic penguin) B decays and preliminary sin(2 beta) measurements by BaBar and Belle (new world average: sin(2 beta) = 0.48 +0.22 -0.24). The updated constraints lead to the Standard Model predictions sin(2 beta) = 0.68 +/- 0.03(exp) +/- 0.04(th), sin(2 alpha) = -0.43 +/- 0.15(exp) +/- 0.20(th), gamma = 56 +/- 5(exp)(+5 -6)(th) deg, Delta m_{Bs} = 16.2 (+2.7 -0.3)(exp)(+1.5 -1.0)(th) ps^{-1}.