The Unreasonable Success of CKM Theory

CKM theory has scored novel successes recently, namely vindication of weak univer-sality and its first decisive test in CP studies. While this does not weaken the case for New Physics, one cannot count on the latter to induce large discrepancies in future studies. To establish smallish deviations one needs precise predictions; those in turn require accurate CKM parameters. I list strategies for extracting V (cb), V (ub) and V (td). After short comments on New Physics in semileptonic B decays and on ∆Γ(B s) I review the CP phenomenology in B decays and stress that a comprehensive program of studying flavour dynamics has to form an essential complement of our next adventure, uncovering the physics behind the electroweak phase transition. The quark masses and CKM parameters control a plethora of observables in flavour dynamics ; originating from nondiagonal quark mass matrixes, they presumably reflect dynamics at high, possibly even GUT scales. As long as flavour dynamics are described by a single SU(2) group, the CKM matrix V CKM has to be unitary leading to the following constraints: k V * (ik)V (kj) = δ ij. The three relations with i = j describe 'weak universality', the six with i = j can be represented by triangles in the complex plane. There are four independent physical parameters: three angles and one complex phase. The latter is the sole source of CP violation (except for the 'strong CP problem') and implies that all six triangles despite their vastly different shapes have the same area: area = 1 2 J , J = |Im[V * (ub)V (ud)V (td) * V (tb)]|. Among these triangles there is one, which controls B decays and is usually referred to as the CKM triangle (UT). Due to the 'long' B lifetime the lengths of its three sides are all O(sin 3 θ C) implying its three angles are 'naturally' large. Since CKM theory with its few parameters undertakes to describe a huge body of data on flavour dynamics, it implies correlations between many a priori unrelated observables, in particular CP sensitive and insensitive quantities. The last point means that one can infer the size of the UT's angles, which control CP asymmetries, from the lengths of their sides, which have no direct sensitivity to CP violation.