ATLAS results on $J/ψp$ resonances in the $Λ_b→J/ψpK$ decays

A study of J/psi p resonances in the Lambda_b -> J/psi p K decays with large m(pK) invariant masses is presented by the ATLAS experiment at the LHC. The analysis is based on a combined sample of pp collision data at centre-of-mass energies of 7 TeV and 8 TeV corresponding to integrated luminosities of 4.9 fb-1 and 20.6 fb-1, respectively. Although the data prefer the model with two or more pentaquark states, the model without pentaquarks is not excluded. The pentaquark masses and widths obtained using the model with two pentaquarks are consistent with those from the LHCb experiment.