Observation of a new Ξb0 state

Le résumé fourni par la source

Using a proton-proton collision data sample collected by the LHCb experiment, corresponding to an integrated luminosity of $8.5\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$, the observation of a new excited ${\mathrm{\ensuremath{\Xi}}}_{b}^{0}$ resonance decaying to the ${\mathrm{\ensuremath{\Xi}}}_{b}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$ final state is presented. The state, referred to as ${\mathrm{\ensuremath{\Xi}}}_{b}(6227{)}^{0}$, has a measured mass and natural width of $m({\mathrm{\ensuremath{\Xi}}}_{b}(6227{)}^{0})=6227.{1}_{\ensuremath{-}1.5}^{+1.4}\ifmmode\pm\else\textpm\fi{}0.5\text{ }\text{ }\mathrm{MeV}$ and $\mathrm{\ensuremath{\Gamma}}({\mathrm{\ensuremath{\Xi}}}_{b}(6227{)}^{0})=18.{6}_{\ensuremath{-}4.1}^{+5.0}\ifmmode\pm\else\textpm\fi{}1.4\text{ }\text{ }\mathrm{MeV}$, where the uncertainties are statistical and systematic. The production rate of the ${\mathrm{\ensuremath{\Xi}}}_{b}(6227{)}^{0}$ state relative to that of the ${\mathrm{\ensuremath{\Xi}}}_{b}^{\ensuremath{-}}$ baryon in the kinematic region $2<\ensuremath{\eta}<5$ and ${p}_{\mathrm{T}}<30\text{ }\text{ }\mathrm{GeV}$ is measured to be $\frac{{f}_{{\mathrm{\ensuremath{\Xi}}}_{b}(6227{)}^{0}}}{{f}_{{\mathrm{\ensuremath{\Xi}}}_{b}^{\ensuremath{-}}}}\mathcal{B}({\mathrm{\ensuremath{\Xi}}}_{b}(6227{)}^{0}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Xi}}}_{b}^{\ensuremath{-}}{\ensuremath{\pi}}^{+})=0.045\ifmmode\pm\else\textpm\fi{}0.008\ifmmode\pm\else\textpm\fi{}0.004,$ where $\mathcal{B}({\mathrm{\ensuremath{\Xi}}}_{b}(6227{)}^{0}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Xi}}}_{b}^{\ensuremath{-}}{\ensuremath{\pi}}^{+})$ is the branching fraction of the decay, and ${f}_{{\mathrm{\ensuremath{\Xi}}}_{b}(6227{)}^{0}}$ and ${f}_{{\mathrm{\ensuremath{\Xi}}}_{b}^{\ensuremath{-}}}$ represent fragmentation fractions. Improved measurements of the mass and natural width of the previously observed ${\mathrm{\ensuremath{\Xi}}}_{b}(6227{)}^{\ensuremath{-}}$ state, along with the mass of the ${\mathrm{\ensuremath{\Xi}}}_{b}^{\ensuremath{-}}$ baryon, are also reported. Both measurements are significantly more precise than, and consistent with, previously reported values.

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