In particle physics
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
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 DsJ(2632) state, seen in the SELEX experiment, was suggested as a possible tetraquark candidate.
References and external links