More precisely, because of the relation between spin and statistics, a particle containing an odd number of fermions is itself a fermion. See also: List of particles § Composite particlesĬomposite particles (such as hadrons, nuclei, and atoms) can be bosons or fermions depending on their constituents. Elementary fermions Standard Model of particle physics For example, at low temperatures, fermions show superfluidity for uncharged particles and superconductivity for charged particles.Ĭomposite fermions, such as protons and neutrons, are the key building blocks of everyday matter.Įnglish theoretical physicist Paul Dirac coined the name fermion from the surname of Italian physicist Enrico Fermi. Weakly interacting fermions can also display bosonic behavior under extreme conditions. However, in the current state of particle physics, the distinction between the two concepts is unclear. Fermions are usually associated with matter, whereas bosons are generally force carrier particles. Then, at least one property of each fermion, such as its spin, must be different.
Suppose multiple fermions have the same spatial probability distribution. Īs a consequence of the Pauli exclusion principle, only one fermion can occupy a particular quantum state at a given time. Therefore, what is usually referred to as the spin-statistics relation is, in fact, a spin statistics-quantum number relation. In addition to the spin characteristic, fermions have another specific property: they possess conserved baryon or lepton quantum numbers. In contrast, particles with half-integer spin are fermions. For example, according to the spin-statistics theorem in relativistic quantum field theory, particles with integer spin are bosons. Some fermions are elementary particles (such as electrons), and some are composite particles (such as protons). Fermions differ from bosons, which obey Bose–Einstein statistics. Fermions include all quarks and leptons and all composite particles made of an odd number of these, such as all baryons and many atoms and nuclei. In addition, these particles obey the Pauli exclusion principle.
Generally, it has a half-odd-integer spin: spin 1 / 2, spin 3 / 2, etc. In particle physics, a fermion is a particle that follows Fermi–Dirac statistics. A composite particle ( hadron) may fall into either class depending on its composition All subatomic particles must be one or the other. Fermions form one of the two fundamental classes of subatomic particle, the other being bosons.
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