Sterile neutrinos are hypothetical particles (neutrino leptons – neutrinos) that are believed to interact only through gravity, and not through other basic interactions in the standard model.
Highlights
The term sterile neutrinos is used to distinguish active neutrinos from known active neutrinos in standard models with weak isospin charges. This usually represents a right-handed chiral neutrino that can be added to the standard model. Particles with the quantum number and mass of sterile neutrinos large enough not to interfere with the current theory of big bang nucleosynthesis are often referred to as neutral heavy neutrons or neutral neutrons.
Since the known active neutrinos are left-handed and all other known fermions have been observed to be left- and right-handed chirality, the existence of right-handed neutrinos is theoretically well established. They were also able to naturally explain the small active mass of neutrinos obtained from neutrino oscillations. The mass of the right-handed neutrino itself is unknown and can have values ??of less than 1 eV at 1015 GeV. To be consistent with leptogenesis and dark matter theory, there must be at least three types of sterile neutrinos, if any. This contrasts with the number of active neutrino types needed to ensure that there are no anomalies in the weakly charged interaction, which is exactly 3 which is the number of charged leptons and quarks.
Search for Sterile Neutrino
The sterile neutrinos search is an active area of ??fundamental particle physics. If present and the mass is less than the energy of the particle in the experiment, it can be obtained in the laboratory by mixing active and sterile neutrinos or through collision of high-energy particles. If they were heavier, the only direct observable result of their presence would be the mass of the observed active neutrinos. However, it can be responsible for a number of phenomena not accounted for in physical cosmology and astrophysics, including dark matter, weak pressure generation, or hypothetical dark radiation. Physicists from the MiniBooNE experiment reported a stronger-than-expected neutrino oscillation signal, which could indicate a sterile neutrino. However, the results of the MicroBooNE experiment did not indicate the presence of sterile neutrinos in the year 2021.
Dark Matter and Sterile Neutrinos
A particle must have a non-zero mass and no electromagnetic charge for it to be considered a candidate for dark matter. Of course, because of these two properties, particles like neutrinos acts as a source for searching for dark matter. Today, it is more common that the theory is based on a model of cold dark matter (the dark matter of the early universe is not relativistic) rather than hot dark matter (the dark matter of the early universe is not relativistic). Therefore, due to its small mass, the active neutrinos of the Standard Model are probably not the cause of all dark matter. Since the mass of sterile neutrinos is currently unknown, the possibility of dark matter cannot be ruled out. If dark matter is composed of sterile neutrinos, certain restrictions can be imposed on their properties. First, the mass of sterile neutrinos must be on the keV scale to generate the structure of the universe observed today. Second, dark matter does not have to be stable, but the lifetime of the particles must be longer than the age of the universe today. This puts an upper limit on the mixing strength of sterile and active neutrinos in the locking mechanism. Sterile neutrinos are a promising candidate for dark matter because of what is known about particles, but like other proposed dark matter particles, their existence has not yet been confirmed.