2020/06/30 by LHCb collaboration, R. Aaij, C. Abellán Beteta +964 · 2 citations
Physics and Astronomy · #hep-ex
paper · pdf · doi:10.1016/j.scib.2020.08.032
published as Science Bulletin 65 (2020) 1983 · All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2020-011.html (LHCb public pages)
arxiv created 2020/11/10 · arxiv updated 2020/12/17
Using proton-proton collision data at centre-of-mass energies of √(s) = 7, 8 and 13 TeV recorded by the LHCb experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 9 fb-1, the invariant mass spectrum of J/ψ 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.