Evidence for B⁰ → ρ⁰ ρ⁰ Decays and Implications for the Cabibbo-Kobayashi-Maskawa Angle α

Authors

B. Aubert, Laboratoire de Physique des Particules, IN2P3/CNRS et Universite´ de Savoie, F-74941 Annecy-Le-Vieux, France
Kenneth A. Bloom, University of Nebraska-LincolnFollow
BaBar Collaboration

Date of this Version

3-16-2007

Comments

Published by American Physical Society. Phys. Rev. Lett. 98, 111801 (2007). http://prl.aps.org. Copyright © 2007 American Physical Society. Permission to use.

Abstract

We search for the decays B⁰ → ρ⁰ ρ⁰, B⁰ → ρ⁰f⁰(980), and B⁰ → f⁰(980)f⁰(980) in a sample of about 384 × 10⁶ Υ (4S)→ BB̅ decays collected with the BABAR detector at the PEP-II asymmetric-energy ℯ⁺ ℯ^- collider at Stanford Linear Accelerator Center. We find evidence for B⁰ → ρ⁰ ρ⁰ with 3.5σ significance and measure the branching fraction Ɓ = 1.07 ± 0:33 ± 0:19) × 10^-6 and longitudinal polarization fraction f_L = 0.87 ± 0.13 ± 0.04, where the first uncertainty is statistical, and the second is systematic. The uncertainty on the Cabibbo-Kobayashi-Maskawa quark-mixing matrix unitarity angle α due to penguin contributions in B→ ρρ decays is 18° at the 1σ level. We also set upper limits on the B⁰ → ρ⁰f⁰(980) and i>B⁰ → f⁰(980)f⁰(980) decay rates.