What is a sterile neutrino?

Sterile neutrinos are hypothetical neutral leptons that interact solely via gravity, distinguishing them from active neutrinos that engage in the weak interaction. Their existence could explain small active neutrino masses and phenomena like dark matter, though experimental results remain mixed. To comply with theories of leptogenesis and dark matter, at least three flavors of sterile neutrinos must exist if they are real.

What we know

• Sterile neutrinos are hypothetical neutral right-handed leptons that interact only through gravity and not via other fundamental interactions of the Standard Model. [1, 2]
• The mass of right-handed sterile neutrinos is unknown and could range anywhere between 1015 GeV/c2 and less than 1 eV/c2. [2]
• If sterile neutrinos exist, there must be at least three flavors of them to comply with theories of leptogenesis and dark matter. [2]
• The MiniBooNE experiment reported a stronger neutrino oscillation signal than expected in May 2018, hinting at sterile neutrinos, while the MicroBooNE experiment in October 2021 showed no evidence of them. [2]

Still open

• It remains unproven whether sterile neutrinos actually exist, given that experiments like MiniBooNE hinted at them while MicroBooNE found no evidence.
• The exact mass of sterile neutrinos is unknown, with theoretical estimates spanning a massive range.

Where to go next

• compared withHow do active neutrinos differ from sterile ones?
• what followedWhat role could sterile neutrinos play in dark matter?
• how it workedHow do neutrino oscillation signals reveal new particles?
• the bigger pictureWhat are heavy neutral leptons?
• how we knowWhat did the MicroBooNE experiment discover about neutrinos?
• an unexpected connectionCould invisible particles explain the origin of dark matter?Particles that completely ignore standard forces except gravity are being investigated as a primary solution to the mystery of cosmic dark matter.

Sources

• [1]sterile neutrino (Wikidata Q1339405) · CC0 1.0
• [2]Sterile neutrino · CC BY-SA 4.0
• [3]Matter · CC BY-SA 4.0
• [4]Coherent elastic neutrino-nucleus scattering · CC BY-SA 4.0
• [5]Muon · CC BY-SA 4.0