neutronneutrino

The neutronneutrino is a hypothetical particle that appears in some speculative extensions of the Standard Model. In these discussions, the term denotes a neutral fermion or a putative bound state associated with the neutron, distinct from the well-established neutron and the standard flavors of neutrinos. The concept is not part of mainstream particle physics and has no confirmed experimental support.

Theoretical interpretations of the idea vary. One view treats a neutronneutrino as a possible bound state formed by a neutron and a neutrino, creating a composite, electrically neutral object with a nonzero baryon number. Another view posits a sterile or weakly interacting neutrino that couples to nucleons in a way that makes it effectively behave as a neutron-neutrino state under certain interactions. In these models, the neutronneutrino might mix with active neutrinos and participate in weak processes, albeit with suppressed or novel couplings.

Properties of the neutronneutrino are speculative. Mass could span a wide range, from very light to heavier scales depending on the underlying model. It is generally assumed to be a spin-1/2 particle and electrically neutral, with the Dirac or Majorana nature varying by framework. Interactions are expected to be weak or mediated by new forces beyond the Standard Model, with couplings constrained by existing neutron experiments and cosmological observations.

Experimental status remains unsettled. There is no confirmed detection of a neutronneutrino. Constraints come from precision measurements of neutron beta decay and lifetimes, searches for anomalous decay channels, and cosmological bounds on extra light relics. A discovery would have profound implications for neutron physics, lepton-baryon interactions, and our understanding of neutrino properties.