Measurement of $CP$-Violating Asymmetries in $B^0\to D^{(*)\pm }{D}^{\mp }$

We present updated measurements of $CP$-violating asymmetries in the decays $B^0\to D^{*\pm }{D}^{\mp }$ and $B^0\to D^{+}{D}^{-}$ using $(383\pm 4)\times {10}^{6}B\overline{B}$ pairs collected by the BABAR detector at the SLAC PEP-II $B$ factory. We determine the time-integrated $CP$ asymmetry ${\mathcal{A}}_{D^{*\pm }{D}^{\mp }}=0.12\pm 0.06\pm 0.02$, and the time-dependent asymmetry parameters to be $C_{D^{*+}{D}^{-}}=0.18\pm 0.15\pm 0.04$, $S_{D^{*+}{D}^{-}}=-0.79\pm 0.21\pm 0.06$, $C_{D^{*-}{D}^{+}}=0.23\pm 0.15\pm 0.04$, $S_{D^{*-}{D}^{+}}=-0.44\pm 0.22\pm 0.06$, $C_{D^{+}{D}^{-}}=0.11\pm 0.22\pm 0.07$, and $S_{D^{+}{D}^{-}}=-0.54\pm 0.34\pm 0.06$, where the first uncertainty is statistical and the second is systematic.

Figure 1

Measured distribution of $m_{\mathrm{ES}}$ for (a) $B^0\to D^{*+}{D}^{-}$, (b) $B^0\to D^{*-}{D}^{+}$, and (c) $B^0\to D^{+}{D}^{-}$ candidates. The solid line is the projection of the fit result and the dotted line represents the background components.

Figure 2

The distributions of $\Delta t$ and fit projections for $B^0\to D^{*+}{D}^{-}$ (left), $B^0\to D^{*-}{D}^{+}$ (middle), and $B^0\to D^{+}{D}^{-}$ (right) candidates in the signal region $m_{\mathrm{ES}}>5.27\mathrm{GeV}/c^2$ with a $B^0$ or $\overline{B}0$ tag (a)–(c). The raw time-dependent asymmetries $(N_{B^0}-N_{{\overline{B}}^0})/(N_{B^0}+N_{{\overline{B}}^0})$ as functions of $\Delta t$ are also shown (d)–(e).