Observation of B+ → ρ+K0 and measurement of its branching fraction and charge asymmetry

Abstract

We present the first observation of the decay B + → ρ + K 0 , using a data sample of 348 fb − 1 collected at the Υ ( 4 S ) resonance with the BABAR detector. The branching fraction and charge asymmetry are measured to be ( 8.0 + 1.4 − 1.3 ± 0.6 ) × 10 − 6 and ( − 12.2 ± 16.6 ± 2.0 ) % , respectively, where the first uncertainty is statistical and the second is systematic. The charge asymmetry is defined by A ch = ( Γ B − − Γ B + ) / ( Γ B − + Γ B + ) with Γ B ± the B ± decay rate. The significance of the observed branching fraction, including systematic uncertainties, is 7.9 standard deviations.