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Scales tilt against five-quark particles

From Tampa, at a meeting of the American Physical Society

May the best data win. In the past 2 years, evidence has quickly mounted for the existence of pentaquarks, never-before-seen subatomic particles theoretically composed of five quarks or antiquarks, which are fundamental constituents of matter. Lately, however, evidence against pentaquarks has been mounting even faster, reports Curtis A. Meyer of Carnegie Mellon University in Pittsburgh.

Physicists have long known that types of quarks and antiquarks combine in twos and threes to form more-complex particles such as protons and neutrons. Until recently, however, no one had ever observed combinations of more than three of the quark or antiquarks.

That all changed when a Russian theorist and his colleagues convinced a team at the Japanese particle accelerator SPring-8 in Hyogo to reexamine data from a 2001 study whose conditions might have generated pentaquarks called theta+.

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