lisäneutriinot

Lisäneutriinot, also known as sterile neutrinos, are hypothetical elementary particles that do not interact via the weak nuclear force, unlike the known active neutrinos. They are "sterile" because they do not participate in the usual interactions that define the Standard Model of particle physics. The existence of sterile neutrinos is not experimentally confirmed, but they are proposed as a potential solution to several outstanding problems in physics.

One of the primary motivations for introducing sterile neutrinos is their possible role in explaining neutrino oscillations. Neutrino oscillations are the phenomenon where neutrinos change between their three known "flavors" (electron, muon, and tau). Some experimental results, like the LSND experiment, hinted at the existence of additional neutrino states that could account for these observed oscillations, leading to the concept of a "four-neutrino mixing scheme" that includes sterile neutrinos.

Another area where sterile neutrinos are invoked is in cosmology and astrophysics, particularly in the context of dark matter. If sterile neutrinos exist with appropriate masses, they could be stable enough to constitute a component of dark matter, the invisible substance that makes up a significant portion of the universe's mass. Depending on their mass, they could be either "warm" or "cold" dark matter, with implications for the structure formation in the universe.

The search for sterile neutrinos is ongoing, employing various experimental techniques. These include looking for specific signatures in neutrino oscillation experiments, searching for evidence of their decay products, and analyzing cosmological data for indirect signs of their existence. However, to date, no definitive evidence for sterile neutrinos has been found, and their existence remains a theoretical possibility.