First Observation of a Baryonic B[superscript 0][subscript s]

Abstract

We report the first observation of a baryonic B[superscript 0][subscript s] decay, B[subscript 0][subscript s] →p[bar over Λ]K[superscript -], using proton-proton collision data recorded by the LHCb experiment at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0 fb[superscript -1]. The branching fraction is measured to be B(B[superscript 0][subscript s] →p[bar over Λ]K[superscript -])+B(B[subscript 0][subscript s]→[bar over p]ΛK[superscript +])=[5.46±0.61±0.57±0.50(B)±0.32(f[subscript s]/f[subscript d])]×10[superscript -6], where the first uncertainty is statistical and the second systematic, the third uncertainty accounts for the experimental uncertainty on the branching fraction of the B[superscript 0]→p[bar over Λ]π[superscript -] decay used for normalization, and the fourth uncertainty relates to the knowledge of the ratio of b-quark hadronization probabilities f[subscript s]/f[subscript d].