FERMIONS

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General Description

 

Fermions are spin -1/2 particles and therefore obey the Fermi-Dirac statistics. They are grouped into two classes: leptons and quarks. Leptons do not interact through the strong nuclear force. Quarks interact through all the fundamental forces of Nature.

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Leptons and quarks are the basic building blocks of matter. Around us, there are no free quarks, as a consequence of the confining property of the strong nuclear force. Free quarks were likely to be present in the primordial plasma of the early Universe, when the temperature was above the QCD phase transition, TQCD ∼ 200 MeV.

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Today we observe bound states: baryons, consisting of three quarks, and mesons, which are bound states of a quark and an antiquark. Baryons and mesons are called hadrons, which was a term coined to indicate particles subject to the strong nuclear force and therefore different from leptons. Protons and neutrons are baryons made of the lightest quarks. Electrons are the lightest leptons with a non-vanishing electric charge. [2]

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Fermions are a class of elementary particles in particle physics that obey the Pauli Exclusion Principle, a fundamental principle of quantum mechanics. This principle states that no two identical fermions can occupy the same quantum state simultaneously, which leads to the familiar behaviour of matter in our everyday world.