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Fermions differ from bosons, which obey Bose–Einstein statistics. Some fermions are elementary particles (such as electrons), and some are composite particles (such as protons). For example, according to the spin-statistics theorem in relativistic quantum field theory, particles with integer spin are bosons.
Composite particles (such as hadrons, nuclei, and atoms) can be bosons or fermions depending on their constituents. Since bosons have integer spin and fermions odd half-integer spin, any composite particle made up of an even number of fermions is a boson. Composite bosons include: All mesons of every type
Bosons are one of the two fundamental particles having integral spinclasses of particles, the other being fermions. Bosons are characterized by Bose–Einstein statistics and all have integer spins. Bosons may be either elementary, like photons and gluons, or composite, like mesons. According to the Standard Model, the elementary bosons are:
All elementary particles are either bosons or fermions. These classes are distinguished by their quantum statistics: fermions obey Fermi–Dirac statistics and bosons obey Bose–Einstein statistics. [1] Their spin is differentiated via the spin–statistics theorem: it is half-integer for fermions, and integer for bosons.
There are two main categories of identical particles: bosons, which can share quantum states, and fermions, which cannot (as described by the Pauli exclusion principle). Examples of bosons are photons, gluons, phonons, helium-4 nuclei and all mesons. Examples of fermions are electrons, neutrinos, quarks, protons, neutrons, and helium-3 nuclei.
A composite boson is a bound state of fermions such that the combination gives a boson. [1] Examples include Cooper pairs, semiconductor excitons, mesons, superfluid helium, Bose–Einstein condensates, atomic bosons, and fermionic condensates. A composite particle containing an even number of fermions is a boson, since it has integer spin.
When considering extensions of the Standard Model, the s-prefix from sparticle is used to form names of superpartners of the Standard Model fermions , [3] e.g. the stop squark. The superpartners of Standard Model bosons have an -ino (bosinos) [3] appended to their name, e.g. gluino, the set of all gauge superpartners are called the gauginos.
The particle representation was first treated in detail by Paul Dirac for bosons and by Pascual Jordan and Eugene Wigner for fermions. [ 1 ] : 35 The Fock states of bosons and fermions obey useful relations with respect to the Fock space creation and annihilation operators .