Study of $\bar{B^{0}} \to D^{(*)0} π^+ π^-$ Decays

Abstract

We report on a study of $\bar{B^{0}} \to D^{(*) 0} π^+ π^-$ decays using 29.1 fb$^{-1}$ of $e^{+}e^{-}$ annihilation data recorded at the $Υ(4S)$ resonance with the Belle detector at the KEKB storage ring. Making no assumptions about the intermediate mechanism, the branching fractions for $\bar{B}^0 \to D^0 π^+ π^-$ and $\bar{B}^0 \to D^{* 0} π^+ π^-$ are determined to be $(8.0 \pm 0.6 \pm 1.5) \times 10^{-4} $ and $ (6.2 \pm 1.2 \pm 1.8) \times 10^{-4}$ respectively. An analysis of $\bar{B^{0}} \to D^{0} π^+ π^-$ candidates yields to the first observation of the color-suppressed hadronic decay $\bar{B}^0 \to D^0 ρ^0$ with the branching fraction $(2.9 \pm 1.0 \pm 0.4) \times 10^{-4}$. We measure the ratio of branching fractions ${\mathcal B}(\bar{B^0} \to D^0 ρ^0) / {\mathcal B}(\bar{B^0} \to D^0 ω)$ = 1.6 $\pm$ 0.8.