Observation of an Excess of Dicharmonium Events in the Four-Muon Final State with the ATLAS Detector

Collaboration
Apr 18, 2023

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Abstract: (APS)
A search is made for potential ccc¯c¯ tetraquarks decaying into a pair of charmonium states in the four muon final state using proton-proton collision data at s=13TeV, corresponding to an integrated luminosity of 140fb-1 recorded by the ATLAS experiment at LHC. Two decay channels, J/ψ+J/ψ4μ and J/ψ+ψ(2S)4μ, are studied. Backgrounds are estimated based on a hybrid approach involving Monte Carlo simulations and data-driven methods. Statistically significant excesses with respect to backgrounds dominated by the single parton scattering are seen in the di-J/ψ channel consistent with a narrow resonance at 6.9 GeV and a broader structure at lower mass. A statistically significant excess is also seen in the J/ψ+ψ(2S) channel. The fitted masses and decay widths of the structures are reported.
Note:
  • p p: colliding beams
  • resonance: production
  • mass: width
  • (4muon): final state
  • p p: scattering
  • J/psi(3100): pair production
  • J/psi(3100): leptonic decay
  • muon: pair production
  • numerical calculations: Monte Carlo
  • ATLAS