Cp Violation: the past as Prologue

CP violation is now measured by three numbers: ǫ and ǫ for the K system and sin2β for B. A future measurement of the analogue of ǫ for the B system would end any possibility of a Superweaklike Theory. Future frontiers in CP violation are briefly discussed. 1 ǫ and ǫ for the K System C, P, and T have played a major role in particle physics over the last fifty years. I like to say that these were theoretical discoveries, not postulates. The starting point was assumed Hamiltonians, in particular QED, which were found to have these symmetries. When Fermi invented the weak interaction in 1933, he modeled it after QED and so it had these symmetries, although this was not emphasized for a long time. In the 1950’s it was pointed out that it was easy to invent interactions that violated these symmetries. However, every local relativistic interaction was found to be invariant under C times P times T. Thus, when P violation was found in 1957, the V-A interaction that explained it violated P and C but left CP and T invariant. Then in 1964, CP violation was discovered in the decay KL −→ 2π. Thirty-six years later the only CP or T violation known was in the K systems. Now we have the first observation of CP violation in the B system. The first observation could be explained as due to CP violation in K −K0 mixing. If we set K = CP times K then the CP eigenstates are