Observation of the Xi−_b into 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 Xi−b into psi(2S)Xi− and measurement of the branching ratio of Xi−b into psi(2S)Xi− to Xi−b into J/psi Xi− are presented. The J/psi and psi(2S) 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 sqrt(s) = 13 TeV in 2016–2018, corresponding to an integrated luminosity of 140 fb−1. The branching fraction ratio is measured to be B(Xi−b to psi(2S)Xi−)/B(Xi−b to J/psi Xi−) = 0.84+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 Xib(5945)0 baryon mass and natural width are also presented, using the Xi−b pi+ final state, where the Xi−b baryon is reconstructed through the decays J/psi Xi−, psi(2S)Xi−, J/psi Lambda K−, and J/psi Sigma0K−. Finally, the fraction of Xi−b baryons produced from Xib(5945)0 decays is determined.