How did physicists detect the neutrino?

A neutrino is one of those enigmatic quantum particles. They're electrically neutral, have a half spin and a very tiny mass, which is the reason that these little devils have eluded detection up until recently. Neutrinos are created in the sun and are a product of proton-proton chain reaction fusion in the sun's core to form helium-2, which decays to deuterium, a positron and an electron neutrino.
Wolfgang Pauli first postulated the neutrino in 1930, but as is often the case, no one believed him. Enrico Fermi named the particle and it was Wang Ganchang who proposed using beta capture to detect neutrinos. Neutrinos were created and detected in 1934 but it took forty years for the people who did this work to be rewarded with a Nobel Prize. I'm sure that has something to do with World War II and the secrecy surrounding atomic bomb development.
The Solar Neutrino Problem came out of the fact that the number of electron neutrinos arriving from the sun was one third to one half the number predicted by the Standard Solar Model (a mathematical treatment of the sun). This Standard Model discrepancy was based on the fact that neutrinos were not supposed to oscillate or have mass and when both of these ideas were determined to be wrong the problem was solved.
There are three flavors of neutrinos: electron, muon and tau. There are also antineutrinos associated with each of these flavors. I am concerned with the electron neutrino because it's what is passing through the Earth at a prodigious level; 65 billion of them pass through every square centimeter of the Earth's surface. Yes, billions of them pass through our bodies every moment. If that's the case, why are they so difficult to detect? The reason for this is because of their infinitesimal mass and size. It's equivalent to trying to shoot and hit a tiny speck of dust in a stacked pile of hay. The other reason they're hard to detect is the fact that they're neutral and therefore don't ionize anything when they hit it.
So, how did they detect them? The answer is by putting the detector underground to shield against cosmic rays and natural radiation. One kind of detector is a huge container of heavy water (water made from deuterium instead of hydrogen). The heavy water contains a scintillator (a chemical that emits UV light when its electrons are hit by an energetic quantum particle like a neutrino). Sensitive UV detectors record these events.
This amazing feat of science was accomplished in 2014 by the Borexino Collaboration detector at the Laboratori Nazionali del Gran Sasso in Italy. The detector was buried 3,800 meters under a mountain. Now they're hunting for the particle associated with Dark Matter, which is an even more ambitious project. Other detectors in Japan have found a neutrino from the sun, verifying their existence. This is how science works in collaboration to determine what's going on in nature.

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