Observation of a new Ξ0 𝑏 state

Using a proton-proton collision data sample collected by the LHCb experiment, corresponding to an integrated luminosity of 8.5  fb−1, the observation of a new excited Ξ0𝑏 resonance decaying to the Ξ−𝑏⁢𝜋+ final state is presented. The state, referred to as Ξ𝑏⁢(6227)0, has a measured mass and natural width of m⁡(Ξ𝑏⁢(6227)0)=6227.1+1.4−1.5±0.5  MeV and Γ⁡(Ξ𝑏⁢(6227)0)=18.6+5.0
−4.1±1.4  MeV, where the uncertainties are statistical and systematic. The production rate of the Ξ𝑏⁢(6227)0 state relative to that of the Ξ−𝑏 baryon in the kinematic region 2<𝜂<5 and 𝑝T<30  GeV is measured to be 𝑓Ξ𝑏⁢(6227)0𝑓Ξ−𝑏
⁢ℬ⁡(Ξ𝑏⁢(6227)0→Ξ−𝑏⁢𝜋+)=0.045±0.008±0.004, where ℬ⁡(Ξ𝑏⁢(6227)0→Ξ−𝑏⁢𝜋+) is the branching fraction of the decay, and 𝑓Ξ𝑏⁢(6227)0 and 𝑓Ξ−𝑏 represent fragmentation fractions. Improved measurements of the mass and natural width of the previously observed Ξ𝑏⁢(6227)− state, along with the mass of the Ξ−
𝑏 baryon, are also reported. Both measurements are significantly more precise than, and consistent with, previously reported values.