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 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 9fb−1, and is found to be

m(Ω−b)−m(Ξ−b)=248.54±0.51(stat)±0.38(syst)MeV/c2.

The mass of the Ω−b baryon is measured to be

m(Ω−b)=6045.9±0.5(stat)±0.6(syst)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 13TeV and corresponding to an integrated luminosity of 6fb−1. Reconstructing beauty baryons in the kinematic region 2<η<6 and pT<20GeV/c with their decays to a J/ψ meson and a hyperon, the ratio

fΩ−bfΞ−b×B(Ω−b→J/ψΩ−)B(Ξ−b→J/ψΞ−)=0.120±0.008(stat)±0.008(syst),

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.