Measurement of the B-0 -> D*- D-s(*+) and D-s(+)-> phi pi(+) branching fractions

We present measurements of the branching fractions B(B-0 -> D*- D-s(*+)) and B(D-s(+) -> phi pi(+)), based on 123 x 10(6) Upsilon(4S) -> B (B) over bar 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(B-0 -> D*- D-s(*+)) and the decay chain is fully reconstructed to measure the branching fraction product B(B-0 -> D*- D-s(*+)) x B(D-s(+) -> phi pi(+)). Comparing these two measurements provides a model-independent determination of the D-s(+) -> phi pi(+) branching fraction. We obtain B(B-0 -> D*- D-s(*+)) = (1.88 +/- 0.09 +/- 0.17)% and B(D-s(+) -> phi pi(+)) = (4.81 +/- 0.52 +/- 0.38)%, where the first uncertainties are statistical and the second systematic.