Observation of a New Ξb- Resonance

From samples of p p collision data collected by the LHCb experiment at √{s }=7 , 8 and 13 TeV, corresponding to integrated luminosities of 1.0, 2.0 and 1.5 fb^-1, respectively, a peak in both the Λ_b⁰K^- and Ξ_b⁰π^- invariant mass spectra is observed. In the quark model, radially and orbitally excited Ξ_b^- resonances with quark content b d s are expected. Referring to this peak as Ξ_b(6227)^-, the mass and natural width are measured to be m_Ξb(6227)^-=6226.9 ±2.0 ±0.3 ±0.2 MeV /c² and Γ_Ξb(6227)^-=18.1 ±5.4 ±1.8 MeV /c² , where the first uncertainty is statistical, the second is systematic, and the third, on m_Ξb(6227)^-, is due to the knowledge of the Λ_b⁰ baryon mass. Relative production rates of the Ξ_b(6227)^- →Λ_b⁰K^- and Ξ_b(6227)^- →Ξ_b⁰π^- decays are also reported.