Observation of the Xi_b- -> psi(2S) Xi- decay and studies of the Xi_b(5945)0 baryon in proton-proton collisions at sqrt(s) = 13 TeV

The first observation of the decay Ξ−b→ψ⁡(2⁢S)⁢Ξ− and measurement of the branching ratio of Ξ− b→ψ⁡(2⁢S)⁢Ξ− to Ξ−b→J/ψ⁢Ξ− are presented. The J/ψ and ψ⁡(2⁢S) mesons are reconstructed using their dimuon decay modes. The results are based on proton-proton colliding beam data from the LHC collected by the CMS experiment at √s=13 TeV in 2016–2018, corresponding to an integrated luminosity of 140 fb−1. The branching fraction ratio is measured to be B⁡(Ξ− b→ψ⁡(2⁢S)⁢Ξ−)/B⁡(Ξ−b→J/ψ⁢Ξ−)=0.8⁢4+0.21−0.19⁢(stat)±0.10⁢(syst)±0.02⁢(B), where the last uncertainty comes from the uncertainties in the branching fractions of the charmonium states. New measurements of the Ξb⁢(5945)0 baryon mass and natural width are also presented, using the Ξ− b⁢π+ final state, where the Ξ−b baryon is reconstructed through the decays J/ψ⁢Ξ−, ψ⁡(2⁢S)⁢Ξ−, J/ψ⁢Λ⁢K−, and J/ψ⁢Σ0⁢K−. Finally, the fraction of Ξ−b baryons produced from Ξb⁢(5945)0 decays is determined.