Neutrino oscillations observation
Do they get masses from a different source than other particles (e.g. Comparison of the numbers of electron and muon neutrinos detected in T2K allows the mixing angle to be measured.
But remember that within each mass state there are different flavour states. Around the same time, the SNO experiment definitively showed that electron neutrinos born in the core of the sun, transition to a mixture of all three flavors, explaining the fewer-than-expected number of electron neutrinos detected on Earth. These developments shared the 2015 Nobel Prize in Physics "for the discovery of neutrino oscillations, which shows that neutrinos have mass.
In other words, when a weak interaction produces a flavor state, such as a muon neutrino, that state is a mixture of states with different mass. The next big neutrino experiment is the T2K experiment in Japan. But in 1967, there was no known mechanism included in the standard model that would allow neutrinos to oscillate between different flavours.
Muon neutrinos and muons are the subsequent decay products. T2K consists of three main components: a proton accelerator at J-PARC which produces the neutrino beam; a suite of near detectors at J-PARC which measure the properties of the neutrinos before they've had a chance to change flavour; and a far detector, Super-Kamiokande, which measures the neutrino properties 295 km later.
Or do they exhibit "CP violation", an asymmetry between matter and antimatter?
While increasingly powerful accelerators with proton beams approaching 1 megawatt of power are being used to produce neutrinos, enormous detectors with tons (for near/short base line detectors ~100 m away from the source) or kilotons (for far detectors ~1000 km from the source) of mass are needed in order to obtain enough observations of neutrino interactions to make precise measurments of neuttrino properties, including neutrino oscillations.
Neutrino-Nuclear Cross-sections: In order to make enormous neutrino detectors, we have turned to cheap and abundant materials that nonetheless allow us to observe neutrino interactions by detecting the particles which come out of them.
Are they the reason for why the universe is matter dominated?
Detecting Neutrinos
BIG detector: One of the defining properties of neutrinos is their extremely feeble interaction with other particles. To this end, we need to accurately understand how a neutrino interacts with the nuclei in the detector material (e.g.
This possibility of flavor change, namely that a neutrino is created in one flavor and interacts some time later as another, is the primary manifestation of neutrino oscillations.
Big Questions
The observation of neutrino oscillations in 1998 by the Super-Kamiokande experiment, established that neutrinos have non-zero and non-degenerate masses.
In the diagrams, the initial state is on the left and the final state is on the right. The beam then carries on through 150 m of rock, which stops the muons, leaving a pure neutrino beam. An originally pure muon neutrino beam can oscillate into an electron neutrino beam and back over space and time. The masses of the different neutrino mass states are not the same, and so within a given flavour state, the different mass states travel at different speeds.
This distance is necessary for the "standard" neutrinos at an energy of ~600 MeV to exhibit their maximum neutrino oscillation effects. This experiment first observed muon neutrino to electron neutrino oscillations, setting the groundwork for ongoing and future searches for CP violation in the form of an imbalance in the oscillation probabilities between this mode of neutrino oscillations and its antimatter counterpart.