# Observation of a New ${\Xi }_{b}^{-}$ Resonance

16 August 2018

Abstract: 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 $1.5\text{}\text{}{\mathrm{fb}}^{-1}$, respectively, a peak in both the ${\Lambda }_{b}^{0}{K}^{-}$ and ${\Xi }_{b}^{0}{\pi }^{-}$ invariant mass spectra is observed. In the quark model, radially and orbitally excited ${\Xi }_{b}^{-}$ resonances with quark content $bds$ are expected. Referring to this peak as ${\Xi }_{b}\left(6227{\right)}^{-}$, the mass and natural width are measured to be ${m}_{{\Xi }_{b}\left(6227{\right)}^{-}}=6226.9±2.0±0.3±0.2\text{}\text{}\mathrm{MeV}/{c}^{2}$ and ${\Gamma }_{{\Xi }_{b}\left(6227{\right)}^{-}}=18.1±5.4±1.8\text{}\text{}\mathrm{MeV}/{c}^{2}$, where the first uncertainty is statistical, the second is systematic, and the third, on ${m}_{{\Xi }_{b}\left(6227{\right)}^{-}}$, is due to the knowledge of the ${\Lambda }_{b}^{0}$ baryon mass. Relative production rates of the ${\Xi }_{b}\left(6227{\right)}^{-}\to {\Lambda }_{b}^{0}{K}^{-}$ and ${\Xi }_{b}\left(6227{\right)}^{-}\to {\Xi }_{b}^{0}{\pi }^{-}$ decays are also reported.

Published in: Physical Review Letters 121 (2018)