neutroninen

Neutroninen is a hypothetical neutral fermion proposed in some speculative extensions of the Standard Model as a light, baryon-like state. The term is not widely used in mainstream literature, and there is no experimental evidence for such a particle. In proposed scenarios, the neutroninen would be electrically neutral, carry spin 1/2, and interact only weakly with ordinary matter, making it difficult to detect with conventional detectors. Its mass is model-dependent, with estimates ranging from a few keV to a few GeV. Some versions place it as a member of a hidden or dark sector that communicates with the Standard Model primarily through weak mixing or portal interactions.

Theoretical motivation often centers on addressing questions related to baryon number conservation, neutron–antineutron oscillations, or as a test particle for baryogenesis mechanisms. In many formulations, the neutroninen would be stable on laboratory timescales, or decay very slowly into standard particles such as neutrinos and photons, depending on the available channels and conservation laws assumed in the model.

Experimental status: There are no confirmed observations of a neutroninen. Experimental searches have constrained possible production rates and lifetimes in nuclear decays, neutron experiments, collider missing-energy analyses, and cosmological data supporting or limiting its existence. Ongoing and future experiments in precision beta decay, neutron physics, and dark-sector probes continue to probe the parameter space for such a particle.

See also: neutrino, neutron, baryon-number conservation, dark sector, portal models, neutron–antineutron oscillation.