Top quark
From Freepedia
The top quark is a third-generation quark with a charge of +(2/3)e. Although all quarks are described in a similar way by the theory of Quantum Chromodynamics, the top quark is by far the most massive: as of 2005 the mass of the top quark is measured to be about 173 GeV (nearly as heavy as a gold nucleus). Because of this, it decays so quickly that it does not hadronize (offering a rare opportunity to study a "bare" quark); thus the experimental signature of the top is the signature of the particles it almost always decays into: a bottom quark and a W boson. It has been suggested that the unexpectedly high mass is an indicator of Supersymmetry.
The top quark was discovered in 1995 at Fermilab, whose Tevatron accelerator remains the only particle accelerator energetic enough to produce top quarks.
On its discovery, a valiant effort was made by many particle physicists to name it "Truth", paired along with "Beauty". Poetic license gave way to pragmatics, and the quarks were named Top and Bottom instead.
External links
- Top quark information on Fermilab website
- Logbook pages from CDF and DZero collaborations' top quark discovery
| edit | |
| Fermions: Quarks | Leptons | |
| Quarks: Up | Down | Strange | Charm | Bottom | Top | |
| Leptons: Electron | Muon | Tau | Neutrinos | |
| Gauge bosons: Photon | W+, W- and Z0 bosons | Gluons | |
| Not yet observed: Higgs boson | Graviton | Other hypothetical particles | |
