Observation of structure in the J/ψ-pair mass spectrum

LHCb Collaboration

Research output: Contribution to journalArticlepeer-review

223 Scopus citations


Using proton-proton collision data at centre-of-mass energies of √s = 7; 8 and 13 TeV recorded by the ffiffi LHCb experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 9 fb-1, the invariant mass spectrum of J/w pairs is studied. A narrow structure around 6:9 GeV=c2 matching the lineshape of a resonance and a broad structure just above twice the J/ψ mass are observed. The deviation of the data from nonresonant J/ψ-pair production is above five standard deviations in the mass region between 6:2 and 7:4 GeV=c2, covering predicted masses of states composed of four charm quarks. The mass and natural width of the narrow X(6900) structure are measured assuming a Breit-Wigner lineshape.

Original languageEnglish (US)
Pages (from-to)1983-1993
Number of pages11
JournalScience Bulletin
Issue number23
StatePublished - Dec 15 2020


  • Exotics
  • Particle and resonance production
  • QCD
  • Quarkonium
  • Spectroscopy
  • Tetraquark

ASJC Scopus subject areas

  • General


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