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

The first observation of the Λb0→Ds−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 Λb0→Λc+π− decay as the normalisation mode, the branching fraction of the Λb0→Ds−p decay is measured to be B(Λb0→Ds−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 Λb0→Λc+π− , Ds−→K−K+π− and Λc+→pK−π+ decays. [Figure not available: see fulltext.]