$\mathrm{CP}$-violating asymmetries calculated from the Breit-Wigner approximation for unstable particle propagators violate $\mathrm{CPT}$ invariance. A formalism satisfying $\mathrm{CPT}$ invariance and unitarity is presented. Applications are given to $t$ decays. For the decay $t\to b{\nu }_{\tau }\overline{\tau }$ in a class of $\mathrm{CP}$-violating Higgs models the $\mathrm{CP}$-violating asymmetry turns out to be ${10}^{-4\mathrm{}}$ times smaller than the previously reported results.

• Received 17 September 1992

DOI:https://doi.org/10.1103/PhysRevD.47.R1741