Precision measurement of the mass and lifetime of the Ξ−b Baryon

We report on measurements of the mass and lifetime of the Ξ−b baryon using about 1800 Ξ−b decays reconstructed in a proton-proton collision data set corresponding to an integrated luminosity of 3.0 fb−1 collected by the LHCb experiment. The decays are reconstructed in the Ξ−b→Ξ0cπ−, Ξ0c→pK−K−π+ channel and the mass and lifetime are measured using the Λ0b→Λ+cπ− mode as a reference. We measure M(Ξ−b)−M(Λ0b)=178.36±0.46±0.16 MeV/c2, (τΞ−b/τΛ0b)=1.089±0.026±0.011, where the uncertainties are statistical and systematic, respectively. These results lead to a factor of 2 better precision on the Ξ−b mass and lifetime compared to previous best measurements, and are consistent with theoretical expectations