Tests of CPT invariance for neutral-flavoured-meson--antimeson mixing

We focus on two aspects of CPT invariance in neutral-meson--antimeson ($M^0 \bar M^0$) mixing: 1. Tests of CPT invariance, using only the property of ``lack of vacuum regeneration'', which occurs as a part of the well-known Lee--Oehme--Yang (LOY) theory; 2. Methods for extracting the CPT-violating mixing parameter $\theta$ through explicit calculations by using the LOY-type theory fully. In the latter context, we demonstrate the importance of the C-even $| M^0 \bar M^0>$ state. In particular, by measuring the time dependence of opposite-sign dilepton events arising from decays of the C-even and C-odd $| M^0 \bar M^0>$ states, $\theta$ may be disentangled from the parameters $\lambda_+$ and $\bar \lambda_-$ characterizing violations of the $\Delta F = \Delta Q$ rule. Furthermore, these two parameters may also be determined. The same is true if one uses like-sign dilepton events arising from only the C-even $| M^0 \bar M^0>$ state.