New Structures in the J/ψJ/ψ Mass Spectrum in Proton-Proton Collisions at √s = 13 TeV

Abstract

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.