Tetra quarks (from Greek tetra, four) are hypothetical meson composed of four quarks (two quarks and two antiquarks ). You like the pentaquark to exotic hadrons, that is such a hypothetical hadrons that do not like the known mesons of two quarks ( quark-antiquark ) or baryons are composed of three quarks. Tetra quarks can be excluded by the present state of knowledge in the theory of strong interactions, quantum chromodynamics, not. They have been proposed several times to interpret resonances were measured in accelerator experiments. So far, however, no conclusive evidence has been provided for their existence.

Several states in the energy of the charmonium, which were observed at Belle and BaBar experiment on, have been interpreted as tetra quark. An example of this is the resonance X ( 3872 ) with a mass of 3872 MeV / c ², which was discovered in 2003 by the Belle experiment.

2010 announced a group of German and Pakistani physicist ( Ahmed Ali and Christian Hambrock of DESY, Jamil Aslam from the Quaid -i -Azam University ) the possible discovery of a tetra quarks, which was made possible by re-analysis of data from the Belle experiment from 2008. At that time ( quantum chromodynamics ) several orders of magnitude higher decay rates of the way we thought, excited bottomonium state Y (5S ) were observed in lower states to produce a pair of charged pions from the theoretical expectations. Ali, Aslam Hambrock and interpret the output state as tetra quark of two light - or quarks and two heavy - or quarks. The authors state, to be able to reproduce the masses and decay rates well with their model. However, there are alternative explanations.

Message about the discovery of quarks Tetra 2013