Cp and CPT Violation in Neutral Kaon Decays

The study of CP violation in neutral K decays has been, from the outset, the primary goal of high-luminosity ϕ-factory, like DAPHNE. At the beginning, attention was focussed almost exclusively on the measurement of the direct CP-violation parameter, ε'/ε. Due to the very interesting work of Buchanan et al. 1, it has been realized that, in addition, a ϕ-factory offers the unique possibility to make a clean test of the CPT symmetry, at the level of precision of 10^-4 or so, and which is indipendent from possible conspiracies, still allowed in the presently measured quantities. The aim of the present article is to provide a self-consistent introduction to the phenomenology of CP and CPT violation in neutral Kaon decays and to give a first illustration of the impact of DAPHNE on the issue of the CPT symmetry. More details are provided in the subsequent papers in this Chapter², 3. Present calculations of ε'/ε in the Standard Theory are also retrieved here, while CP violation in charged Kaon decays is deferred to a later part of this Report⁴. Of course, there exist in the literature many excellent reviews of the subject, starting from the classical and influential article of Lee and Wu⁵. In the more recent literature, CPT symmetry in Kaon decays has been analyzed by Barmin et al. 6 and, with reference to the experiments at a ϕ-factory, in reff. 7. 1.