Precision Measurement of the Mass and Lifetime of the Ξb− Baryon

We report on measurements of the mass and lifetime of the Ξb− baryon using about 1800 Ξb− 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 Ξb− → Ξc0 π−, Ξc0 → p K− K− π+ channel and the mass and lifetime are measured using the Λ0b → Λc+ π− mode as a reference. We measure M(Ξb−) − M(Λ0b) = 178.36 ± 0.46 ± 0.16 MeV/c2, (τ_Ξb−/τ_Λ0b) = 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 Ξb− mass and lifetime compared to previous best measurements, and are consistent with theoretical expectations