The standard model class the elementary particles in two big families: the fermions and the Bosons. The fermions are the particles with Spin half-entirety (i.e. 1/2, 3/2, 5/2,…) : the electron, the Muon, the Neutrino and the Quark S are fermions.
The fermions gather in two families:
- the Lepton S, which are not subjected to the strong Interaction;
- the Quark S, which are subjected to all the interactions of nature.
The other fermions all are made up.
See also: Lepton
In the family of the leptons, one knows:
- the electron : this stable particle is of mass 1836 times less than that of the Proton, and of negative load - E;
- the Muon : this unstable particle with the same load that the electron and is 210 times more massive than this last. Left with itself, the muon disintegrates in 2,197×10 -6 S by the means of the weak Interaction, leaving in its place an electron, a Neutrino μ and a antineutrino;
- the Tauon : this very unstable particle is of the same load than the electron, while its Masse is of 3500 times higher to him. It disintegrates into 10 -13 S, leaving in its place a neutrino τ and a antineutrino;
- the Neutrino : lightest of the fermions. It has only one weak load (whereas the electron has also an electric charge). It does not have almost any interaction with the matter. There exist three types of neutrinos:
- # the neutrino μ (emitted during the disintegration of a muon);
- # the electronic neutrino E (emitted during disintegration β - transformation of a neutron into proton);
- # the neutrino τ (emitted during the disintegration of the tauon).
- : Because of their low mass (the neutrinos μ and τ have a mass quite lower than that of the electron), these three types of neutrinos are stable. The neutrinos are probably the most abundant particles of the Univers.
See also: Quark
One counts six representatives of the family of the quarks: the quark down (d), the quark up (U), the quark strange (S) and three others, produced in laboratory. The Quark S join by triplets to form Proton S (U, U and d) and Neutron S (D, D and U). Their mass varies, but is in all the cases quite higher than that of the electron. They have a load of the color which subjects them to the strong Interaction, most important of the interactions.
The principle of exclusion of PauliThe principle of exclusion of Pauli formulated in 1925 by Wolfgang Pauli prohibited with two fermions to be at the same place in the same quantum state.
Thus in the atom, all the electrons have different quantum numbers; it is also the case in all the other system of fermions.
Properties of the fermionsOn a quantum scale, the fermions have a dual nature, i.e. it can behave like particles but also like Onde S.
On a macroscopic scale, the fermions seem all particles: it is the case of the electron, the muon and all the other fermions.
It is also noticed that all the fermions have an unspecified load: the neutrino has a weak load, the electron has, moreover, one electric charge and the natural quarks (which are not obtained in laboratory) have at the same time charges electric and weak but also a load of color subjecting it to the strong interaction.
Lastly, if the bosons can be vectors of interactions, it is never the case for the fermions.
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