Neutriinodes

Neutriinodes are a hypothetical category of neutral fermionic excitations associated with an extended neutrino sector in some theories beyond the Standard Model. In these approaches, the observed active neutrinos coexist with additional states that may be gauge singlets or charged under a new symmetry. A neutriinode is described as a neutral, spin-1/2 excitation that can be Majorana or Dirac in nature and may mix with active neutrinos or interact via a new mediator particle. The precise properties of neutriinodes—such as their mass, lifetime, and coupling strengths—depend on the underlying model.

Theoretical motivation for neutriinodes includes addressing the origin of neutrino masses, providing candidates for dark matter, or enabling novel neutrino self-interactions that could influence cosmology and astrophysical processes. Mass scales proposed for neutriinodes span wide ranges, from sub-eV to well above the GeV scale, with couplings to Standard Model particles typically suppressed. Some models treat neutriinodes as intermediate states in seesaw mechanisms, while others imagine them as stable or long-lived particles that could participate in early-Universe dynamics or in rare decays.

Production and interactions of neutriinodes are model dependent. They could be produced in high-energy collisions, meson decays, or during the early stages of the Universe. Their interactions with ordinary matter are expected to be weak, often mediated by mixing with active neutrinos or by new forces. Cosmological and astrophysical considerations place constraints on their properties, particularly through effects on the cosmic microwave background, structure formation, and neutrino observables.

As of now, neutriinodes remain hypothetical with no experimental confirmation. Ongoing and planned experiments in neutrino physics, collider searches, and cosmological observations continue to probe regions of parameter space where neutriinodes could exist. If discovered, they would have implications for neutrino mass generation, lepton-number physics, and potential connections to dark matter. See also sterile neutrinos, Majorana fermions, and beyond-Standard Model neutrino sectors.