What Are Neutrinos?

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able to convert into it’s corresponding changed particle, (electrons, muons, or tau leptons) when it interacts with ordinary matter. The only thing needed to prove this theory was a machine that could detect all three types of neutrinos. In the 1990s Arthur mcDonald began building one in a mine in Ontario. It contained tons of heavy water, that is rare but naturally occurring, when hydrogen containing a single proton, is replaced by it’s cousin, deuterium, which contains a proton and a neutron. All types of neutrinos could scatter off the deuterium in the heavy water, breaking it apart into protons and neutrons, then the neutrons could be counted. They found the amount predicted by the best solar models, which suggests that electron neutrinos can, in fact oscillate into other neutrinos. At the same time, in Tokyo, Takaaki Kajita lead another remarkable experiment. The was a detector in a mine in Japan that could detect neutrinos not from the sun but from the upper atmosphere. As cosmic ray protons collide with the atmosphere, they create showers of other particles, including muon neutrinos. In the mine, the muon neutrinos scattered off of hydrogen nuclei in the water, converting into muons. Also, the detector could observe neutrinos coming in two directions, some traveling downward from the atmosphere, and others traveling upwards having passed through the earth. The rates for the two were different, showing that the neutrinos that had travelled different distances were arriving at the detector as different kinds of neutrinos. They were art different points in their oscillation cycles. This is all very interesting, but it is also very important to modern science. In the standard model of particle physics, the neutrino has to be massless. The discovery that neutrinos have mass shows that something is missing, and that the standard model isn’t complete. There is new physics yet to be discovered. This is why the finding is so important and is worthy of a Nobel Prize.