Theory summary

This talk briefly summarizes the theoretical contributions presented on the previous day of the meeting. Readers are recommended to turn to the contributions on those talks for further details. My job in this talk is to review all the theoretical contributions presented to this meeting. Paul Avery has reviewed the more experimentally oriented contributions to the Physics and Simulation session. Let me begin by stressing some points from my own introductory talk. The major focus of a B-factory must be more than just observing CP violation in one or more channels. The task before us is to test the predictions of the Standard Model, which means that it is important not just to define the Unitarity triangle, but in fact to measure enough separate parameters that the triangle is overconstrained. The consistency or otherwise of the various determinations of the triangle will then provide a check on the consistency of Standard Model predictions. To overconstrain the triangle we must either measure all three angles, or, if we can only measure two angles, then we must in addition measure two sides. The side opposite the angle α is effectively determined by Vcb while that opposite the angle β is fixed by Vub. Thus we need good measurements of both Vcb and Vub. The quantity Vcb can be well measured. Matthias Neubert showed, in his talk, how predictions from heavy quark symmetry can be used cleanly to extract it from B → D*eν decays. The quantity Vub is more difficult. Heavy quark symmetries can again be used, here to relate semileptonic decays of the B or B* (to π or ρ and eν) to similar decays of the D and D*