Observation of new structure in the J/psi J/psi mass spectrum in proton-proton collisions at sqrt(s) = 13 TeV

A search is reported for near-threshold structures in the J/ψJ/ψ invariant mass spectrum produced in proton-proton collisions at √s=13  TeV from data collected by the CMS experiment, corresponding to an integrated luminosity of 135  fb−1. Three structures are found, and a model with quantum interference among these structures provides a good description of the data. A new structure is observed with a local significance above 5 standard deviations at a mass of 6638+43−38(stat)+16−31(syst)  MeV. Another structure with even higher significance is found at a mass of 6847+44−28(stat)+48−20(syst)  MeV, which is consistent with the X(6900) resonance reported by the LHCb experiment and confirmed by the ATLAS experiment. Evidence for another new structure, with a local significance of 4.7 standard deviations, is found at a mass of 7134+48−25(stat)+41−15(syst)  MeV. Results are also reported for a model without interference, which does not fit the data as well and shows mass shifts up to 150 MeV relative to the model with interference.