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

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Schmelling,  M.
Division Prof. Dr. James A. Hinton, MPI for Nuclear Physics, Max Planck Society;

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Citation

LHCb Collaboration, Aaij, R., Abellan Beteta, C., Adeva, B., Adinolfi, M., Aidala, C. A., et al. (2020). Observation of structure in the J/ψ-pair mass spectrum. Science Bulletin, 65(23), 1983-1993. doi:10.1016/j.scib.2020.08.032.


Cite as: https://hdl.handle.net/21.11116/0000-0008-2AF2-8
Abstract
Using proton-proton collision data at centre-of-mass energies of root 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/psi pairs is studied. A narrow structure around 6.9 GeV/c(2) matching the line-shape of a resonance and a broad structure just above twice the J/psi mass are observed. The deviation of the data from nonresonant J/psi-pair production is above five standard deviations in the mass region between 6.2 and 7.4 GeV/c(2), 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. (C) 2020 Science China Press. Published by Elsevier B.V. and Science China Press.