First observation and branching fraction measurement of the Λb⁰→Ds⁻p decay

The first observation of the Λ⁰b →D⁻ₛp 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⁻ₛp decay is measured to be ℬ (Λ⁰b →D⁻ₛp) = (12.6 ±0.5±0.3 ±1.2) x 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 → p K⁻π⁺ decays.