Tetraquark
In particle physics a tetraquark is a hypothetical meson composed of four valence quarks. In principle, a tetraquark state may be allowed in quantum chromodynamics, the modern theory of strong interactions. However, there has been no confirmed report of a tetraquark state to date. Any established tetraquark state would be an example of an exotic hadron which lies outside the quark model classification.
In 2003 a particle temporarily called X(3872), by the Belle experiment in Japan, was suggested as a tetraquark candidate[1] as it was originally conjectured in.[2] The name X is a temporary name, indicating that there are still some questions about its properties to be tested. The number following is the mass of the particle in MeV.
In 2004, the DsJ(2632) state seen in Fermilab's SELEX was suggested as a possible tetraquark candidate.
In 2009, Fermilab announced that they have discovered a particle temporarily called Y(4140), which may also be a tetraquark[3]
There are as well indications that the Y(4660), discovered by Belle in 2007, could be a tetraquark state, as discussed in [4]
In 2010, two physicists from DESY and a physicist from Quaid-i-Azam University re-analyzed former experimental data and announced that, in connection with the ϒ(5S) meson (a form of bottomonium), a well-defined tetraquark resonance exists.[5][6]
See also
References
- ^ D. Harris (13 April 2008). "The charming case of X(3872)". Symmetry Magazine. http://www.symmetrymagazine.org/breaking/2008/04/13/the-charming-case-of-x3872/. Retrieved 2009-12-17.
- ^ L. Maiani, F. Piccinini, V. Riquer and A.D. Polosa (2005). "Diquark-antidiquarks with hidden or open charm and the nature of X(3872)". Physical Review D 71: 014028. arXiv:hep-ph/0412098. Bibcode 2005PhRvD..71a4028M. doi:10.1103/PhysRevD.71.014028.
- ^ http://www.universetoday.com/2009/03/18/new-particle-throws-monkeywrench-in-particle-physics/
- ^ G. Cotugno, R. Faccini, A.D. Polosa and C. Sabelli (2010). "Charmed Baryonium". Physical Review Letters 104 (13): 132005. Bibcode 2010PhRvL.104m2005C. doi:10.1103/PhysRevLett.104.132005.
- ^ http://physicsworld.com/cws/article/news/42475
- ^ A. Ali, C. Hambrock, M.J. Aslam (2010). "Tetraquark Interpretation of the BELLE Data on the Anomalous Υ(1S)π+π- and Υ(2S)π+π- Production near the Υ(5S) Resonance". Physical Review Letters 104 (16): 162001. Bibcode 2010PhRvL.104p2001A. doi:10.1103/PhysRevLett.104.162001.
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