Disentangling violations ofCPTfrom other new-physics effects

We analyze the prospects for observing $\mathrm{CPT}$ violation using neutral-meson $P^0-P^0¯$ systems. Before one can claim a measurement of $\mathrm{CPT}$ violation, one must be able to rule out the possibility that its result is due to simpler new-physics effects. In particular, one must be able to separate the $\mathrm{CPT}$-violating quantities from parameters violating the $\Delta P=\Delta Q$ rule of semileptonic decays, and from new-physics contributions to the production mechanism of the neutral mesons. One can isolate $\mathrm{CPT}$ violation using the semileptonic decays of single, tagged neutral mesons; unfortunately, this situation cannot be implemented at the ${\rm Y}\mathrm{}\left(4S\right).$ For $P^0{P}^0¯$ pairs produced in a correlated parity-odd state we show that, by combining the di-lepton with the single-lepton decays, it is in principle possible to extract unambiguously one $\mathrm{CPT}$-violating parameter. Finally, we develop the formalism necessary for describing new-physics effects in the production mechanism; this includes both cascade decays and violations of the rule of associated production.