Observation of the Ξb- → ψ(2S)Ξ- decay and studies of the Ξb (5945)0 baryon in proton-proton collisions at √s=13 TeV

The first observation of the decay Xi(-)(b) -> psi(2S)Xi(-) and measurement of the branching ratio of Xi(-)(b) -> psi(2S)Xi(-) to Xi(-)(b) -> 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 root 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) -> psi(2S)Xi(-))/B(Xi(-)(b) -> J/psi Xi(-)) = 0.84(-0.19)(+0.21)(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 Xi(b) (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 Sigma K-0(-). Finally, the fraction of Xi(-)(b) baryons produced from Xi(b) (5945)(0) decays is determined.