Measurement of the mass difference and relative production rate of the ${\mathrm{\Omega }}_b^{-}$ and ${\mathrm{\Xi }}_b^{-}$ baryons

The mass difference between the ${\mathrm{\Omega }}_b^{-}$ and ${\mathrm{\Xi }}_b^{-}$ baryons is measured using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of $9{\text{fb}}^{-1}$, and is found to be \begin{equation} m(Ω^-_b)- m(Ξ^-_b) = 248.54 \pm 0.51 $\text{(stat)}$ \pm 0.38 $\text{(syst)}$ , $\text{MeV}$/c^2. \end{equation} The mass of the ${\mathrm{\Omega }}_b^{-}$ baryon is measured to be \begin{equation} m(Ω^-b)= 6045.9 \pm 0.5 $\text{(stat)}$ \pm 0.6 $\text{(syst)}$ , $\text{MeV}$/c^2. \end{equation} This is the most precise determination of the ${\mathrm{\Omega }}_b^{-}$ mass to date. In addition, the production rate of ${\mathrm{\Omega }}_b^{-}$ baryons relative to that of ${\mathrm{\Xi }}_b^{-}$ baryons is measured for the first time in $pp$ collisions, using an LHCb dataset collected at a center-of-mass energy of $13\text{TeV}$ and corresponding to an integrated luminosity of $6{\text{fb}}^{-1}$. Reconstructing beauty baryons in the kinematic region $2<\eta <6$ and $p_T<20\text{GeV}\mathrm{/}c$ with their decays to a $J\mathrm{/}\psi$ meson and a hyperon, the ratio \begin{equation} \frac{f{Ω^-b}}{f{Ξ^-_b}}\times\frac{$\mathcal{B}$(Ω^-_b \to J/ψΩ^-)}{$\mathcal{B}$(Ξ^-_b \to J/ψΞ^-)} = 0.120 \pm 0.008 $\text{(stat)}$ \pm 0.008 $\text{(syst)}$, \end{equation} is obtained, where $f_{{\mathrm{\Omega }}_b^{-}}$ and $f_{{\mathrm{\Xi }}_b^{-}}$ are the fragmentation fractions of $b$ quarks into ${\mathrm{\Omega }}_b^{-}$ and ${\mathrm{\Xi }}_b^{-}$ baryons, respectively, and $\mathcal{B}$ represents the branching fractions of their respective decays.