Study of $\text{ }{B}^{0}\ensuremath{\rightarrow}{\mathit{\ensuremath{\rho}}}^{+}{\mathit{\ensuremath{\rho}}}^{\ensuremath{-}}$ decays and implications for the CKM angle ${\mathbit{\ensuremath{\phi}}}_{\mathbit{2}}$

Study of $B^{0} \to ρ^{+} ρ^{-}$ decays and implications for the CKM angle $ϕ_{2}$

P. Vanhoefer et al. (Belle Collaboration)

Phys. Rev. D 93, 032010 – Published 26 February 2016; Erratum Phys. Rev. D 94, 099903 (2016)

Abstract

We present a measurement of the branching fraction and the longitudinal polarization fraction of $B^{0} \to ρ^{+} ρ^{-}$ decays, as well as the time-dependent $C P$ violating parameters in decays into longitudinally polarized $ρ^{+} ρ^{-}$ pairs with Belle’s final data set of $772 \times 10^{6}$ $B \bar{B}$ pairs, at the $ϒ (4 S)$ resonance, collected at the asymmetric-energy $e^{+} e^{-}$ collider KEKB. We obtain $B (B^{0} \to ρ^{+} ρ^{-}) = (28.3 \pm 1.5 (stat) \pm 1.5 (syst)) \times 10^{- 6}$ , $f_{L} = 0.988 \pm 0.012 (stat) \pm 0.023 (syst)$ , $A_{C P} = 0.00 \pm 0.10 (stat) \pm 0.06 (syst)$ , $S_{C P} = - 0.13 \pm 0.15 (stat) \pm 0.05 (syst)$ . We perform an isospin analysis to constrain the Cabibbo-Kobayashi-Maskawa angle $ϕ_{2}$ and obtain two solutions with $ϕ_{2} = (93.7 \pm 10.6) °$ , being most compatible with other Standard-Model based fits to the data.