Photo courtesy of SPring-8 [Click image above for larger view. Use back button to return to this page.]

The paper reports on the evidence for a long-sought subatomic five-quark particle known as a "pentaquark." It contains five components—four quarks and one antiquark. No subatomic particle detected previously contains more than three components. In theory, the existence of such an exotic state is not forbidden, but its properties, especially its narrow width (long life), is very hard to explain. Experimentally, there are as many negative reports as positive ones. The paper is highly cited because the situation is still not settled experimentally and thus remains controversial theoretically. The field of subatomic research is also quite an active one.

If it is confirmed, it will be a confirmation of the first discovery of a "pentaquark".

A nucleus is made up of nucleons (Protons and neutrons). A nucleon consists of three quarks. The basic building block of matter is known to be a quark. Quarks exist only in groups. But a complete description of quark confinement in matter is still not possible. The "pentaquark," a new way of understanding quark-confinement, will broaden our comprehension of the quark-bound state.

In 1997, the Russian theorist Dmitri Diakonov and his colleagues at the Nordic Institute for Theoretical Physics (NORDITA) in Copenhagen predicted the existence of a "pentaquark" with a mass about 50% heavier than that of a hydrogen atom. It was Dr. Diakonov who first suggested that I might begin a search for the "pentaquark" during a luncheon at a conference at the University of Adelaide in March of 2000.