CP Violation in K-Meson Decays

This is a pedagogical review of some selected topics of CP and T violation in the decays of K mesons. Diagonalization of the quark mass matrix and the emergence of the complex phase in both the standard and the left–right symmetric models is considered in great detail. Prominence is given to a correct definition of the CP-violating quantities: $ϵ,{ϵ}^{\mathrm{\prime }}$ {\it etc.} (with due regard for the Wu–Yang phase convention) and to formulation of the time-reversal invariance criterion in the elementary particle physics. A particular attention has been concentrated on theoretical evaluation of the parameters $ϵ$ and ${ϵ}^{\mathrm{\prime }}$ and the CP- and T-violating asymmetries in the decays $K\to \mu \nu \gamma$ and $K\to 3\pi$.