Precision Measurement of the Mass and Lifetime of the Ξb− Baryon

Le résumé fourni par la source

We report on measurements of the mass and lifetime of the ${\mathrm{\ensuremath{\Xi}}}_{b}^{\ensuremath{-}}$ baryon using about 1800 ${\mathrm{\ensuremath{\Xi}}}_{b}^{\ensuremath{-}}$ decays reconstructed in a proton-proton collision data set corresponding to an integrated luminosity of $3.0\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ collected by the LHCb experiment. The decays are reconstructed in the ${\mathrm{\ensuremath{\Xi}}}_{b}^{\ensuremath{-}}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Xi}}}_{c}^{0}{\ensuremath{\pi}}^{\ensuremath{-}}$, ${\mathrm{\ensuremath{\Xi}}}_{c}^{0}\ensuremath{\rightarrow}p{K}^{\ensuremath{-}}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$ channel and the mass and lifetime are measured using the ${\mathrm{\ensuremath{\Lambda}}}_{b}^{0}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}_{c}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ mode as a reference. We measure $M({\mathrm{\ensuremath{\Xi}}}_{b}^{\ensuremath{-}})\ensuremath{-}M({\mathrm{\ensuremath{\Lambda}}}_{b}^{0})=178.36\ifmmode\pm\else\textpm\fi{}0.46\ifmmode\pm\else\textpm\fi{}0.16\text{ }\text{ }\mathrm{MeV}/{c}^{2}$, $({\ensuremath{\tau}}_{{\mathrm{\ensuremath{\Xi}}}_{b}^{\ensuremath{-}}}/{\ensuremath{\tau}}_{{\mathrm{\ensuremath{\Lambda}}}_{b}^{0}})=1.089\ifmmode\pm\else\textpm\fi{}0.026\ifmmode\pm\else\textpm\fi{}0.011$, where the uncertainties are statistical and systematic, respectively. These results lead to a factor of 2 better precision on the ${\mathrm{\ensuremath{\Xi}}}_{b}^{\ensuremath{-}}$ mass and lifetime compared to previous best measurements, and are consistent with theoretical expectations.

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