Study of the Decay ${B}^{0}({\overline{B}}^{0})\ensuremath{\rightarrow}{\ensuremath{\rho}}^{+}{\ensuremath{\rho}}^{\ensuremath{-}}$, and Constraints on the Cabibbo-Kobayashi-Maskawa Angle $\ensuremath{\alpha}$

Study of the Decay $B^{0} ({\bar{B}}^{0}) \to ρ^{+} ρ^{-}$ , and Constraints on the Cabibbo-Kobayashi-Maskawa Angle $α$

B. Aubert et al. (BABAR Collaboration)

Phys. Rev. Lett. 93, 231801 – Published 2 December 2004

Abstract

Using a data sample of $89 \times 10^{6}$ $Υ (4 S) \to B \bar{B}$ decays collected with the BABAR detector at the PEP-II asymmetric $B$ Factory at SLAC, we measure the $B^{0} ({\bar{B}}^{0}) \to ρ^{+} ρ^{-}$ branching fraction as $[30 \pm 4 (s t a t) \pm 5 (s y s t)] \times 10^{- 6}$ and a longitudinal polarization fraction of $f_{L} = 0.99 \pm 0.03 (s t a t)_{- 0.03}^{+ 0.04} (s y s t)$ . We measure the time-dependent-asymmetry parameters of the longitudinally polarized component of this decay as $C_{L} = - 0.17 \pm 0.27 (s t a t) \pm 0.14 (s y s t)$ and $S_{L} = - 0.42 \pm 0.42 (s t a t) \pm 0.14 (s y s t)$ . We exclude values of $α$ between 19° and 71° (90% C.L.).