ABSTRACT
In the standard model, the mixture is due to the so-called box diagram shown in Figure 13.1.1 is diagram provides the main contribution to the mass dierence between BH and BL. e fact that four weak vertices are required explains why the mass dierence is so small (recall that each additional vertex implies a further power of the weak coupling constant
and a further suppression in perturbation theory). is contribution is proportional to (Vtb Vtd*)2. In contrast to the kaon system, this diagram with a large phase from Vtd dominates B0-B0bar mixing, and therefore, it predicts a large CP violation in mixing.
