Sterile neutrinos are a proposed type of neutrino that do not interact via the standard weak nuclear force, unlike the three known “active” neutrino types—electron, muon, and tau neutrinos. Instead, sterile neutrinos would only interact through gravity or possibly other unknown forces, making them extremely difficult to detect.
The idea of sterile neutrinos arises from anomalies in several neutrino experiments, where observed behavior deviates slightly from predictions based on only three active neutrinos. These anomalies suggest the possibility of an additional neutrino flavor—one that is “sterile,” meaning it does not participate in weak interactions.
If they exist, sterile neutrinos could:
- Mix with active neutrinos, causing detectable oscillation patterns.
- Have mass, potentially helping explain the small masses of active neutrinos through a mechanism called the seesaw mechanism.
- Serve as a dark matter candidate, especially if they are relatively light and stable.
Despite extensive searches in experiments like LSND, MiniBooNE, and various reactor and accelerator studies, sterile neutrinos have not yet been confirmed. Their existence would signal physics beyond the Standard Model, making them one of the most intriguing topics in modern particle physics.