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| | Search for Exotic Matter |
 | | All known hadronic matter is composed of two kinds of quark configurations: baryons, such as protons and neutrons, which are combinations of 3 quarks (qqq), and mesons, such as pions, which are combinations of a quark and an anti-quark (q). |
 | | However states of matter consisting of four quarks and an anti-quark (qqqq), called pentaquarks, are allowed by the theory of strong interactions, Quantum Chromodynamics, and have been the subject of experimental searches since the 1980’s. |
 | | Evidence of the exotic baryon, which is expected to decay into a neutron (n) and positive K meson, (Theta+ -> n K+) was sought in a reaction in which an energetic photon interacts with a liquid hydrogen target yielding an uncharged antikaon meson, K0, a charged kaon, K+, and a neutron, n. |
| physics.rice.edu /naturalsciences/physics/blank.cfm?doc_id=8524 (395 words) |
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