Lepton

With leptons (from the Greek λεπτός LEPTOS, thin ',' small ',' fine ' ) refers to a class of elementary particles, which are thought to form together with the quarks and the gauge bosons the fundamental building blocks that make up the matter composed. This is described in the Standard Model of elementary particle physics.

Historically, the name lepton is chosen in contrast to two other classes of particles, namely the meson ( " medium weight ") and the baryons ( "heavy -weight "). Mesons and baryons are among the hadrons. As it turned out, these hadrons consist of two quarks ( mesons ) or three quarks ( baryons ) are composed, not elementary. Among the leptons there are also particles, the " easy " are not. For example, the τ - lepton (or tauon ) is about twice as heavy as a proton. At the time of naming the tauon however, was still unknown.

There are six leptons, which are divided into three so-called generations due to their physical properties. The following table lists the properties of the leptons are summarized.

Leptons are subject to the weak interaction and gravitation. If they carry an electrical charge, they also interact through the electromagnetic interaction. All leptons are fermions and have spin ½.

Electron, muon and tauon carry a negative elementary charge. The neutrinos are not charged, but are distinguished by their flavor ( e, or). For each lepton exists an antiparticle. The anti- neutrinos have no electric charge, the electric charge of the antiparticle of the electron, muon and tauon is a positive elementary charge.

In the event that the flavor eigenstates do not correspond to the mass eigenstates of the neutrinos, the flavor is no longer a conserved quantity. For a neutrino that was produced in the eigenstate e, there is after a certain time a chance to be detected in the state or ( neutrino oscillations ). This model, the deficit of the measured on Earth flux of solar neutrinos explain ( solar neutrino deficit ). These results suggest that neutrinos have a rest mass greater than zero.