The top quark, discovered by the CDF and DZero collaborations at Fermilab in 1995, is the heaviest known elementary particle and the shortest-lived one. Top quarks decay in as little as 10-24 seconds. Any top quarks that were made in the very early universe decayed away billions of years ago. Fortunately, particle accelerators allow scientists to re-create such fleeting visitors to our world, by pumping sufficient amounts of energy into particle collisions to make top-antitop pairs. At present, the only accelerator with sufficient energy to do this is Fermilab's Tevatron collider.
The Standard Model of Particles and Interactions describes very well the properties of and forces among quarks and leptons, but it contains parameters-such as particle masses-whose origins are still unknown. The values of many of these parameters are inter-related by quantum effects that couple particles to each other. In particular, the masses of the top quark and of the weak W boson together constrain the mass of the long hypothesized, but so far never observed, Higgs boson. A precise measurement of the top mass can therefore indicate where to look for the Higgs, and indeed whether the hypothesis of a Standard Model Higgs is consistent with experimental data at all. The Higgs particle is of extreme interest as it couples to all other particles, and according to the Standard Model these interactions are the source of quark and lepton masses - and hence the mass of all matter on earth.
|last modified 6/7/2004 email Fermilab|