Measurement of the B0→D*-D*+s and D+s→ϕπ+ branching fractions

We present measurements of the branching fractions B(B⁰→D^*-D^*+_s) and B(D⁺_s→ϕπ⁺), based on 123×10⁶ Υ(4S)→BB¯ decays collected by the BABAR detector at the PEP-II asymmetric-energy e⁺e^- B factory. A partial reconstruction technique is used to measure B(B⁰→D^*-D^*+_s) and the decay chain is fully reconstructed to measure the branching fraction product B(B⁰→D^*-D^*+_s)×B(D⁺_s→ϕπ⁺). Comparing these two measurements provides a model-independent determination of the D⁺_s→ϕπ⁺ branching fraction. We obtain B(B⁰→D^*-D^*+_s)=(1.88±0.09±0.17)% and B(D⁺_s→ϕπ⁺)=(4.81±0.52±0.38)%, where the first uncertainties are statistical and the second systematic.