Precision measurement of the mass and lifetime of the Ξ⁰_b Baryon

Using a proton-proton collision data sample corresponding to an integrated luminosity of 3 fb^-1 collected by LHCb at center-of-mass energies of 7 and 8 TeV, about 3800 Ξ⁰_b→Ξ⁺_cπ^-, Ξ⁺_c→pK^-π⁺ signal decays are reconstructed. From this sample, the first measurement of the Ξ⁰_b baryon lifetime is made, relative to that of the Λ⁰_b baryon. The mass differences M(Ξ⁰_b) - M(Λ⁰_b) and M(Ξ⁺_c) - M(Λ⁺_c) are also measured with precision more than 4 times better than the current world averages. The resulting values are ^τΞ⁰_b / ^τΛ⁰_b = 1.006±0.018±0.010, M(Ξ⁰_b) − M(Λ⁰_b) = 172.44±0.39±0.17 MeV/c², M(Ξ⁺_c) − M(Λ⁺_c) = 181.51±0.14±0.10 MeV/c², where the first uncertainty is statistical and the second is systematic. The relative rate of Ξ⁰_b to Λ⁰_b baryon production is measured to be ^fΞ⁰_b / ^fΛ⁰_b B(Ξ⁰_b → Ξ⁺_cπ⁻) / B(Λ⁰_b → Λ⁺_cπ⁻) B(Ξ⁺_c → pK⁻π⁺) / B(Λ⁺_c → pK⁻π⁺) = (1.88±0.04±0.03) × 10⁻², where the first factor is the ratio of fragmentation fractions, b → Ξ⁰_b relative to b → Λ⁰_b. Relative production rates as functions of transverse momentum and pseudorapidity are also presented.