Measurement of the mass difference and relative production rate of the Ω −b and Ξ −b baryons

The mass difference between the Ω−b and Ξ−b baryons is measured using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb−1, and is found to be mðΩ−b Þ − mðΞ−
b Þ ¼ 248.54 0.51ðstatÞ 0.38ðsystÞ MeV=c2. The mass of the Ω−
b baryon is measured to be mðΩ−b Þ ¼ 6045.9 0.5ðstatÞ 0.6ðsystÞ MeV=c2. This is the most precise determination of the Ω−b mass to date. In addition, the production rate of Ω−b baryons relative to that of Ξ−b baryons is measured for the first time in pp collisions, using an LHCb dataset collected at a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 6 fb−1. Reconstructing beauty baryons in the kinematic region 2 < η < 6 and p T < 20 GeV=c with their decays to a J=ψ meson and a hyperon, the ratio
fΩ−bfΞ−b× BðΩ−b →J=ψΩ− ÞBðΞ−b →J=ψΞ−Þ ¼ 0.120 0.008ðstatÞ 0.008ðsystÞ, is obtained, where fΩ−b and fΞ−b are the fragmentation fractions of b quarks into Ω−b and Ξ−b baryons, respectively, and B represents the branching fractions of their respective decays.