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    Measurement of the mass difference and relative production rate of the Ωb− and Ξb− baryons

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    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 m ( Ω − b ) − m ( Ξ − b ) = 248.54 ± 0.51 ( stat ) ± 0.38 ( syst )     MeV / c 2 . The mass of the Ω − b baryon is measured to be m ( Ω − b ) = 6045.9 ± 0.5 ( stat ) ± 0.6 ( syst )     MeV / c 2 . 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 p p 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 f Ω − b f Ξ − b × B ( Ω − b → J / ψ Ω − ) B ( Ξ − b → J / ψ Ξ − ) = 0.120 ± 0.008 ( stat ) ± 0.008 ( syst ) , is obtained, where f Ω − b and f Ξ − 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
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