2
views
0
recommends
+1 Recommend
0 collections
0
shares
• Record: found
• Abstract: found
• Article: found
Is Open Access

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

Preprint

Bookmark
There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

### Abstract

Using proton-proton collision data at centre-of-mass energies of $$\sqrt{s} = 7$$, $$8$$ and $$13\mathrm{\,TeV}$$ recorded by the LHCb experiment at the Large Hadron Collider, corresponding to an integrated luminosity of $$9\mathrm{\,fb}^{-1}$$, the invariant mass spectrum of $$J/\psi$$ pairs is studied. A narrow structure around $$6.9\mathrm{\,GeV/}c^2$$ matching the lineshape 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 $$7.4\mathrm{\,GeV/}c^2$$, 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.

### Author and article information

###### Journal
30 June 2020
###### Article
2006.16957