Hints emerge of a four-quark particle.Physicists at accelerators in Japan and the United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. have detected a subatomic particle that may be unlike any seen before. Some evidence suggests that the particle contains two pairs of more fundamental particles--quarks and antiquarks--bound together. If that's verified, then the new find would be the first four-quark particle known. Until recently, quarks Quarks The basic constituent particles of which elementary particles are understood to be composed. Theoretical models built on the quark concept have been very successful in understanding and predicting many phenomena in the physics of elementary particles. and antiquarks were observed only in groups of twos or threes. However, twice this year, researchers have reported possible five-quark particles (SN: 10/18/03, p. 245). The discovery of yet other combinations of quarks and antiquarks could illuminate the force that binds quarks and antiquarks together. Physicists call this the strong force. Experimenters at the High Energy Accelerator Research Organization (KEK See CEC. ) laboratory in Tsukuba, Japan, noted the first signs of the new particle while examining the aftermaths of hundreds of millions of electron-positron collisions. When the KEK investigators stumbled upon the intriguing new particle, they were seeking a previously undiscovered but mundane quark-anti-quark duo--that remains unobserved. A team at Fermi National Accelerator Laboratory Fermi National Accelerator Laboratory (Fermilab), physical science research center located near Batavia, Ill., est. 1968 as the National Accelerator Laboratory, renamed 1974 in honor of Enrico Fermi. It was built on the site of the former village of Weston. (Fermilab) in Batavia, Ill., confirmed the KEK results, which are chronicled in an upcoming Physical Review Letters Physical Review Letters is one of the most prestigious journals in physics.[1] Since 1958, it has been published by the American Physical Society as an outgrowth of The Physical Review. . Some theorists suspect the new find may be deceptive. The calculations that guided the KEK team might have been inadequate for predicting the properties of the duo particle the team was seeking, proposes Fermilab theorist Estia J. Eichten Estia J. Eichten, is a theoretical physicist, of the Fermi National Accelerator Laboratory. He graduated from M.I.T., where he was a student of Roman Jackiw, and was Associate Professor of Physics at Harvard before joining the Fermilab Theoretical Physics Department in 1982. . In that case, the newfound particle could actually be the duo, but with characteristics that only seem unexpected. On the other hand, Eichten notes, the large mass of the new particle closely matches that expected if two quark-antiquark D-mesons got hitched. |
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