Observation of Excited Λ0b Baryons

Abstract

Using pp collision data corresponding to 1.0 fb−1 integrated luminosity collected by the LHCb detector, two narrow states are observed in the Λ0bπ+π− spectrum with masses 5911.97±0.12(stat)±0.02(syst)±0.66(Λ0b mass) MeV/c2 and 5919.77±0.08(stat)±0.02(syst)±0.66(Λ0b mass) MeV/c2. The significances of the observations are 5.2 and 10.2 standard deviations, respectively. These states are interpreted as the orbitally excited Λ0b baryons, Λ*0b(5912) and Λ*0b(5920).