First observation of the charmless decay of $\Xi_b^- \to pK^-K^-$ at LHCb

— We present here the search for Ξb and Ω − b baryon decays to the charmless hadronic final states ph−h′− at the LHCb detector, where h(′) denotes a kaon or pion. The analysis is based on a sample of proton-proton collision data collected at centre-of-mass energies √ s = 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb−1. We observe the decay of Ξb → pK−K− with a significance of 8.7 standard deviations, and evidence at the level of 3.4 standard deviations is found for the Ξb → pK−π− decay. This result is the first ever observation of a Ξb baryon decaying into charmless final state.