Observation of a New Ξb− Resonance

Le résumé fourni par la source

From samples of $pp$ collision data collected by the LHCb experiment at $\sqrt{s}=7$, 8 and 13 TeV, corresponding to integrated luminosities of 1.0, 2.0 and $1.5\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$, respectively, a peak in both the ${\mathrm{\ensuremath{\Lambda}}}_{b}^{0}{K}^{\ensuremath{-}}$ and ${\mathrm{\ensuremath{\Xi}}}_{b}^{0}{\ensuremath{\pi}}^{\ensuremath{-}}$ invariant mass spectra is observed. In the quark model, radially and orbitally excited ${\mathrm{\ensuremath{\Xi}}}_{b}^{\ensuremath{-}}$ resonances with quark content $bds$ are expected. Referring to this peak as ${\mathrm{\ensuremath{\Xi}}}_{b}(6227{)}^{\ensuremath{-}}$, the mass and natural width are measured to be ${m}_{{\mathrm{\ensuremath{\Xi}}}_{b}(6227{)}^{\ensuremath{-}}}=6226.9\ifmmode\pm\else\textpm\fi{}2.0\ifmmode\pm\else\textpm\fi{}0.3\ifmmode\pm\else\textpm\fi{}0.2\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ and ${\mathrm{\ensuremath{\Gamma}}}_{{\mathrm{\ensuremath{\Xi}}}_{b}(6227{)}^{\ensuremath{-}}}=18.1\ifmmode\pm\else\textpm\fi{}5.4\ifmmode\pm\else\textpm\fi{}1.8\text{ }\text{ }\mathrm{MeV}/{c}^{2}$, where the first uncertainty is statistical, the second is systematic, and the third, on ${m}_{{\mathrm{\ensuremath{\Xi}}}_{b}(6227{)}^{\ensuremath{-}}}$, is due to the knowledge of the ${\mathrm{\ensuremath{\Lambda}}}_{b}^{0}$ baryon mass. Relative production rates of the ${\mathrm{\ensuremath{\Xi}}}_{b}(6227{)}^{\ensuremath{-}}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}_{b}^{0}{K}^{\ensuremath{-}}$ and ${\mathrm{\ensuremath{\Xi}}}_{b}(6227{)}^{\ensuremath{-}}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Xi}}}_{b}^{0}{\ensuremath{\pi}}^{\ensuremath{-}}$ decays are also reported.

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