Fermione

Fermione is a term sometimes used in theoretical or fictional contexts to denote a hypothetical elementary fermion. It is not part of the standard nomenclature in real particle physics; in established science, particles with half-integer spin are called fermions, with examples including quarks and leptons, which obey Fermi-Dirac statistics and the Pauli exclusion principle.

In speculative models, a fermione would be an elementary particle with half-integer spin, typically 1/2, and would participate in gauge interactions according to the theory’s charges. Depending on the model, it might interact with known forces, or it could belong to a hidden or dark sector with limited or no direct couplings to Standard Model particles, potentially connecting via portal interactions or gravity.

Possible roles for a fermione include serving as a dark matter candidate, a sterile fermion, or a component of beyond-Standard-Model frameworks that extend the fermionic content of the universe. The mass and couplings of a fermione would be highly model dependent, with theoretical possibilities ranging from very light to very heavy scales, and from weak to strong interactions within its sector.

Experimental status: there is no confirmed observation of a particle specifically named fermione. Searches for new fermions—such as heavy neutral leptons, vector-like fermions, or sterile neutrinos—place constraints on masses and interaction strengths, but do not establish a particle by that name.

See also: Fermion, Pauli exclusion principle, Fermi-Dirac statistics, Standard Model, dark matter candidates. Etymology: the name suggests a relation to fermions, from Enrico Fermi.