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.

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

Lusiani, A.
Membro del Collaboration Group
;
Morello, M. J.
Membro del Collaboration Group
;
Pajero, T.
Membro del Collaboration Group
;
2020

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.
2020
Settore FIS/01 - Fisica Sperimentale
QCD; Exotics; Tetraquark; Spectroscopy; Quarkonium; Particle and resonance production
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11384/101647
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