FERMILAB / SCIENCE PHOTO LIBRARY FERMILAB / SCIENCE PHOTO LIBRARY
Evidence for the top quark. Computer display of particle tracks which provide strong evidence for the existence of the top quark. Top quarks are created in proton-antiproton collisions along with top anti-quarks. A top decays almost instantly into a bottom quark and a W boson. The W then decays into a quark-lepton pair (eg an electron and neutrino). The magenta track has the highest momentum, and is a muon from a W decay. Green and yellow tracks are 'jets' from other quark decays. The red arrow indicates 'missing energy', normally due to one or more neutrinos. These tracks were detected by the D0 experiment at the Fermi National Accelerator Laboratory, USA.
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