Neutriinoton

Neutriinoton is a hypothetical elementary particle proposed in certain extensions of the Standard Model of particle physics. It is described as a neutral, spin-1/2 fermion that acts as a heavy lepton-like cousin of the known neutrinos. In many models, the neutriinoton can be either a Dirac or Majorana particle and may mix with active neutrinos, enabling weak interactions that are suppressed by a small mixing parameter.

Theoretical basis and properties vary by model, but common features include a broad possible mass range and feeble couplings to ordinary matter. The particle is typically envisioned as part of a larger sector that adds sterile or hidden states beyond the three active neutrinos. Depending on the mass and mixing, neutriinotons can have lifetimes ranging from promptly decaying to long-lived on detector scales, producing distinctive experimental signatures.

Phenomenology and potential roles in physics beyond the Standard Model are diverse. If they exist, neutriinotons could affect neutrino mass generation, influence neutrino oscillation patterns, contribute to leptogenesis scenarios that help explain the matter–antimatter asymmetry, and, in some parameter spaces, serve as dark matter candidates or triggers for various rare processes.

Production in experiments may occur via meson decays, Z or Higgs decays, or in high-energy collisions. Detection strategies focus on identifying displaced vertices, characteristic decay products, or missing energy patterns consistent with heavy neutral lepton decays. Experimental searches place constraints on mass–mixing parameter spaces, but no unambiguous discovery has been made to date.

See also: sterile neutrino, heavy neutral lepton, beyond the Standard Model, leptogenesis.