First observation and branching fraction measurement of the Λ0b → D−s p decay

The first observation of the Λ0b → D−s p decay is presented using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of √s = 13 TeV, corresponding to a total integrated luminosity of 6 fb−1. Using the Λ0b → Λ+c π− decay as the normalisation mode, the branching fraction of the Λ0b → D−s p decay is measured to be B(Λ0b → D−s p) = (12.6 ± 0.5 ± 0.3 ± 1.2) × 10−6, where the first uncertainty is statistical, the second systematic and the third due to uncertainties in the branching fractions of the Λ0b → Λ+c π−, D−s → K−K+π− and Λ+c → pK−π+ decays.