Tests of $CPT$ symmetry in $B^0\text{−}{\overline{B}}^0$ mixing and in $B^0\to c\overline{c}{K}^0$ decays

Using the eight time dependences ${\mathrm{e}}^{-\mathrm{\Gamma }t}(1+C_i\cos \mathrm{\Delta }mt+S_i\sin \mathrm{\Delta }mt)$ for the decays $\mathrm{{\rm Y}}(4S)\to B^0{\overline{B}}^0\to f_j{f}_k$, with the decay into a flavor-specific state $f_j={\ell }^{\pm }X$ before or after the decay into a $CP$ eigenstate $f_k=c\overline{c}{K}_{S,L}$, as measured by the BABAR experiment, we determine the three $CPT$-sensitive parameters $\mathrm{Re}(\mathsf{z})$ and $\mathrm{Im}(\mathsf{z})$ in $B^0\text{−}{\overline{B}}^0$ mixing and $|\overline{A}/A|$ in $B^0\to c\overline{c}{K}^0$ decays. We find $\mathrm{Im}(\mathsf{z})=0.010\pm 0.030\pm 0.013$, $\mathrm{Re}(\mathsf{z})=-0.065\pm 0.028\pm 0.014$, and $|\overline{A}/A|=0.999\pm 0.023\pm 0.017$, in agreement with $CPT$ symmetry.