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Fermilab collider experiments discover rare single top quark:
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This proton-antiproton collision, recorded by the DZero collaboration, is among the single top quark candidate events. The top quark decayed and produced a bottom quark jet (b jet), a muon and a neutrino. Credit: DZero collaboration.



This collision event display, created by the CDF collaboration, shows a single top quark candidate event. The red arrow indicates the direction of a neutrino and the purple line the direction of a muon escaping from the decay of the top quark. Credit: CDF collaboration.



Protons and antiprotons comprise quarks, antiquarks and gluons. A proton-antiproton collision can produce a single top quark in two different ways: a quark and an antiquark can create a W boson, which then decays into a top quark and an anti-bottom quark. Or a gluon and a quark interact, with the quark emitting a W boson and the gluon creating a bottom quark and anti-bottom quark. The W boson then interacts with the bottom quark and produces a single top quark. In both cases, the top quark is short-lived and decays, for example, into a bottom quark, a lepton (such as a muon) and a neutrino. Credit: DZero collaboration.



The Fermilab accelerator complex accelerates protons and antiprotons close to the speed of light. The Tevatron collider, four miles in circumference, produces millions of proton-antiproton collisions per second, maximizing the chance for discovery. Two experiments, CDF and DZero, record the collisions to look for signs of new particles and subatomic processes.



The CDF detector, about the size of a 3-story house, weighs about 6,000 tons. Its subsystems record the "debris" emerging from each high-energy proton-antiproton collision produced by the Tevatron. The detector records the path, energy and charge of the particles emerging from the collisions. This information can be used to look for particles emerging from the decay of a short-lived top quark.



The DZero detector records particles emerging from high-energy proton-antiproton collisions produced by the Tevatron. Tracing the particles back to the center of the collision, scientists understand the subatomic processes that take place at the core of proton-antiproton collisions. Scientists search for the tiny fraction of collisions that might have produced single top quarks.



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Last modified: 04/28/2009 |