Observation of excited $\Omega_c^0$ baryons in $\Omega_b^- \to \Xi_c^+ K^-\pi^-$ decays

The first observation of the Ω b - → Ξ c + K - π - decay is reported using p p collision data at center of mass energies of 7, 8, and 13 TeV collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb - 1 . Four excited Ω c 0 baryons are observed in the Ξ c + K - mass projection of the Ω b - → Ξ c + K - π - decays with the significance of each exceeding five standard deviations. They coincide with the states previously observed in prompt p p and e + e - production. Relative production rates, masses, and natural widths of the states are measured, and a test of spin hypotheses is performed. Moreover, the branching ratio of Ω b - → Ξ c + K - π - is measured relative to the Ω b - → Ω c 0 π - decay mode and a precise measurement of the Ω b - mass of 6044.3 ± 1.2 ± 1. 1 - 0.22 + 0.19 MeV is obtained.