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The X(3872) is an exotic meson candidate with a mass of 3871.68 MeV/c2[1] which does not fit into the quark model because of its quantum numbers. It was first discovered in 2003 by the Belle experiment[2] in Japan and later confirmed by several other experimental collaborations. Several theories have been proposed for its nature,[3] such as a mesonic molecule or a diquark-antidiquark pair (tetraquark).

The quantum numbers of X(3872) have been determined by the LHCb experiment at CERN in March 2013. The values for JPC are 1++.[4] The first evidence of X(3872) production in the quark–gluon plasma have been reported by the CMS experiment at CERN in January 2022.[5]

See also[edit]


  1. ^ Particle Data Group Live listings
  2. ^ Choi, S.-K.; et al. (Belle Collaboration) (2003). "Observation of a Narrow Charmoniumlike State in Exclusive B±→K±π+π-J/ψ Decays". Physical Review Letters. 91 (26): 262001. arXiv:hep-ex/0308029. Bibcode:2003PhRvL..91z2001C. doi:10.1103/PhysRevLett.91.262001. PMID 14754041. S2CID 1017547.
  3. ^ Swanson, E. S. (2006). "The new heavy mesons: A status report". Physics Reports. 429 (5): 243–305. arXiv:hep-ph/0601110. Bibcode:2006PhR...429..243S. doi:10.1016/j.physrep.2006.04.003. S2CID 54704359.
  4. ^ Aaij, R.; et al. (LHCb collaboration) (2013). "Determination of the X(3872) meson quantum numbers". Physical Review Letters. 110 (22): 222001. arXiv:1302.6269. Bibcode:2013PhRvL.110v2001A. doi:10.1103/PhysRevLett.110.222001. PMID 23767712.
  5. ^ Sirunyan, A. M.; et al. (CMS collaboration) (2022). "Evidence for X(3872) in Pb-Pb Collisions and Studies of its Prompt Production at 5.02 TeV". Physical Review Letters. 128 (3): 032001. arXiv:2102.13048. doi:10.1103/PhysRevLett.128.032001. PMID 35119878.