The Top Quark:
Production & Decay

The top quark is by far the heaviest quark and was the last to be discovered, it is also a highly unstable particle. Collisions between protons and anti-protons can produce a top quark and an anti-top, which each decay to a W boson and a b quark.
decay modes of the top quark

The circle represents several possible different interactions. The dotted line shows the other particles left over, which continue down the beam pipe.

The W bosons then decay by the lepton mode or the hadron mode. The b quarks decay into hadron jets, referred to as heavy jets due to the high mass of the b quark.

Jets produced by the other, lighter, quarks are referred to as light jets.

  • Events in which both the positively charged W boson and the negatively charged W boson decay by the lepton channel can be known as the 'dilepton' channel.
  • Events in which only one W boson decays by the lepton channel can be known as the single-lepton channel.
  • Events where neither of the W bosons decay by the lepton channel can be referred to as 'all jets' since all the detector sees is hadron jets.
decay modes of the top quark

blue means the decay is hadronic, green means the decay is leptonic

In the dilepton channel, only the total missing transverse momentum can be known, not the individual momentum of each neutrino.

The single lepton channel, where the transverse momentum of the neutrino is known, is the most useful for the task of finding the mass of the W boson.

Last modified Fri 25 January 2002 . View page history
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