Tetraquark seen by DESY researchers

New Scientist : Corrected: 5/6/2010: The tetraquark , a massive particle made up of four quarks, may have been seen at KEK particle accelerator in Tsukuba, Japan.Thirty years ago, tetraquarks were proposed as a solution to the equations of quantum chromodynamics. QCD is a theory developed to describe how quarks combine to make two-quark mesons, such as pions and kaons, and three-quark baryons like protons or neutrons.Possible sightings of tetraquarks have occurred before at KEK, the SLAC National Accelerator Laboratory in Stanford, California, and D-Zero at the Fermilab accelerator in Illinois. It is extremely rare to observe these particles.Ahmed Ali and colleagues at German Electron Synchrotron (DESY) in Hamburg, Germany, found a 2008 data anomaly in KEK’s BELLE experiment , in which the end result from colliding electrons and positrons decayed at too rapid a rate for the suspected particle created. If this particle was a tetraquark, however, then the decay rate would match the experimental results. Related link Tetraquark interpretation of the BELLE data on the anomalous Î¥(1 S) Ï ⁺ Ï ^- and Î¥(2 S) Ï ⁺ Ï ^- production near the Î¥(5 S) resonance