Limit on the B0→ρ0ρ0 Branching Fraction and Implications for the Cabibbo-Kobayashi-Maskawa Angle α

Abstract

We search for the decay B 0 → ρ 0 ρ 0 in a data sample of about 227 × 10 6 Υ ( 4 S ) → B ¯¯¯ B decays collected with the BABAR detector at the PEP-II asymmetric-energy e + e − collider at SLAC. We find no significant signal and set an upper limit of 1.1 × 10 − 6 at 90% C.L. on the branching fraction. As a result, the uncertainty due to penguin contributions on the Cabibbo-Kobayashi-Maskawa unitarity angle α measured in B → ρ ρ decays is decreased to 11° at 68% C.L.