Measurements of Branching Fractions and Time-dependent CP Violating Asymmetries in $B^0\to D^{(\ast )\pm }{D}^{\mp }$ Decays

Abstract

We report measurements of branching fractions and time-dependent CP asymmetries in $B^0\to D^{+}{D}^{-}$ and $B^0\to D^{\ast \pm }{D}^{\mp }$ decays using a data sample that contains $(772\pm 11)\times 10^{6}B\bar{B}$ pairs collected at the $\hat{I}\yen (4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We determine the branching fractions to be $\mathcal{B}(B^0\to D^{+}{D}^{-})=(2.12\pm 0.16\pm 0.18)\times 10^{-4}$ and $\mathcal{B}(B^0\to D^{\ast \pm }{D}^{\mp }=(6.14\pm 0.29\pm 0.50)\times 10^{-4}$. We measure CP asymmetry parameters ${\mathcal{S}}_{D^{+}{D}^{-}}=-1.06_{-0.14}^{+0.21}\pm 0.08$ and ${\mathcal{C}}_{D^{+}{D}^{-}}=-0.43\pm 0.16\pm 0.05$ in $B^0\to D^{+}{D}^{-}$ and ${\mathcal{A}}_{D^{\ast }D}=+0.06\pm 0.05\pm 0.02$, ${\mathcal{S}}_{D^{\ast }D}=-0.78\pm 0.15\pm 0.05$, ${\mathcal{C}}_{D^{\ast }D}=-0.01\pm 0.11\pm 0.04$, $\hat{I}”{\mathcal{S}}_{D^{\ast }D}=-0.13\pm 0.15\pm 0.04$ and $\hat{I}”{\mathcal{C}}_{D^{\ast }D}=+0.12\pm 0.11\pm 0.03$ in $B^0\to D^{\ast \pm }{D}^{\mp }$, where the first uncertainty is statistical and the second is systematic. We exclude the conservation of CP symmetry in both decays at equal to or greater than $4\ddot{I}ƒ$ significance.

7 pages, 2 figures