Measurement of the branching fraction of the $${{B} ^0} { ightarrow }{{D} ^+_{s}} {{pi } ^-} $$ decay

A branching fraction measurement of the B0 -> Ds+pi- decay is presented using proton-proton collision data collected with the LHCb experiment, corresponding to an integrated luminosity of 5.0fb-1. The branching fraction is found to be B(B0 -> Ds+pi-)=(19.4 +/- 1.8 +/- 1.3 +/- 1.2)x10-6, where the first uncertainty is statistical, the second systematic and the third is due to the uncertainty on the B0 -> D-pi+, Ds+-> K+K-pi+ and D--> K+pi-pi- branching fractions. This is the most precise single measurement of this quantity to date. As this decay proceeds through a single amplitude involving a b -> u charged-current transition, the result provides information on non-factorisable strong interaction effects and the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element Vub. Additionally, the collision energy dependence of the hadronisation-fraction ratio fs/fd is measured through Bs0 -> Ds+pi- and B0 -> D-pi + decays.