We report a new sensitive search for $CPT$ violation, which includes improved measurements of the $CPT$-violating parameter $z$ and the total decay-width difference normalized to the averaged width $\Delta {\Gamma }_d/{\Gamma }_d$ of the two $B_d$ mass eigenstates. The results are based on a data sample of $535\times {10}^6$ $B\overline{B}$ pairs collected at the ${\rm Y}(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We obtain $\mathcal{R}e(z)=[+1.9\pm 3.7(\mathrm{stat})\pm 3.3(\mathrm{syst})]\times {10}^{-2}$, $\mathcal{I}m(z)=[-5.7\pm 3.3(\mathrm{stat})\pm 3.3(\mathrm{syst})]\times {10}^{-3}$, and $\Delta {\Gamma }_d/{\Gamma }_d=[-1.7\pm 1.8(\mathrm{stat})\pm 1.1(\mathrm{syst})]\times {10}^{-2}$, all of which are consistent with zero. This is the most precise single measurement of these parameters in the neutral $B$-meson system to date.

• Received 5 March 2012

DOI:https://doi.org/10.1103/PhysRevD.85.071105