Observation of Two New Excited Ξ 0 b States Decaying to Λ 0 b K − π +

Two narrow resonant states are observed in the ??0bK??????? mass spectrum using a data sample of protonproton collisions at a center-of-mass energy of 13 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 6 fb???1. The minimal quark content of the ??0bK??????? system indicates that these are excited ??0b baryons. The masses of the ??b??6327??0 and ??b??6333??0 states are spectively, with a mass splitting of ??m 1/4 5.41??0.26 systematic, and due to the ??0b mass measurement. The measured natural widths of these states are consistent (95%) credibility level. The significance of the two-peak hypothesis is larger than nine (five) Gaussian standard deviations compared to the no-peak (one-peak) hypothesis. The masses, widths, and resonant structure of the new states are in good agreement with the expectations for a doublet of 1D ??0b resonances.