Tetraquark

In particle physics a tetraquark is a hypothetical meson composed of 5 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.

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In 2003 a particle temporarily called X(3872), by the Belle experiment in Japan, was suggested as a tetraquark candidate. 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 D_sJ(2632) state, seen in the SELEX experiment, was suggested as a possible tetraquark candidate.

See also

• Hadrons, quark model, exotic hadrons, pentaquark
• Quantum chromodynamics, color confinement

References and external links

• The Belle experiment
  • Belle press release