Overview of Kaon Physics

In this overview, I discuss some of the open issues in Kaon physics. After briefly touching on lattice calculations of Kaon dynamics and tests of CPT, my main focus of attention is on ǫ ′ /ǫ and on constraints on the CKM model. The impact of rare K-decays and of experiments with B-mesons for addressing the issue of CP-violation is also discussed. The importance of looking for signals of flavor-conserving CP violating phases is emphasized. It is difficult to overview a mature field like Kaon physics. In thinking about the subject, it seemed natural for me to divide my report into three parts. The first of these parts addresses areas of Kaon physics where steady progress continues to be made, but more still needs to be done. Kaon dynamics, as well as tests of conservation laws and of the CKM Model 1 properly belong in this category. The second part encompasses what, colloquially, might be called the " hot topic " of Kaon physics—the new experimental results on ǫ ′ /ǫ and their theoretical interpretation. Finally, in the last part, I grouped together topics in Kaon physics which bring new insights into the future, particularly regarding the nature of flavor. Although CP-violation in B-decays obviously has little to do directly with Kaons its study, along with that of rare Kaon decays, properly belongs in this last category. So does the hunting for new CP violating phases. By contrasting the ratio of the charged to neutral Kaon lifetimes [τ (K +)/τ (K o S) = 138.6 ± 0.4 2 ] with that for B-mesons [τ (B +)/τ (B o) = 1.072 ± 0.026 2 ], it is clear that Kaon decays involve strong interaction dynamics. While B-decays are essentially reflective of the decays of the b-quark, Kaon decays are strongly dependent on the underlying QCD dynamics.