Neutrinos have other weird aspects. They pass right through our entire planet like sunlight passing through a pane of glass. Every second, trillions of neutrinos-some created in the Big Bang, a few spewing from distant supernovas, a few emanating from inside the Sun-stream through our bodies without our noticing. These are elementary particles, forming the basic constituents of ordinary matter: the Lego bricks of the universe.
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This is exotic and fantastic stuff, but why should neutrino oscillations and neutrino masses be worthy of popular, or even scientific, interest? However, a number of oddities about neutrinos had started to become apparent in various experiments that were studying sources of neutrinos.
Because neutrinos interact so weakly, they can travel enormous distances. The neutrinos involved in Pauli’s proposal were electron neutrinos, associated with processes that include electrons.
As worldwide competition in the field of particle physics is intensifying, Japan needs to take measures to improve basic science research, including boosting research funds and creating an environment in which researchers have the freedom to pursue the studies they feel are important and don’t have to worry about job security.
In principle, atmospheric neutrinos of 5 GeV and higher that arrive at a detector directly beneath them preserve their original muon-to-electron ratio of 2:1.
While particle detectors were deciphering the odd behavior of the three neutrinos, mystery was collecting in the heavens.
The realization that neutrinos are produced in the nuclear reactions that power the Sun prompted Bruno Pontecorvo to propose in 1946 that the particle’s feeble interactions could be an advantage: Neutrinos that reached Earth could carry with them information about the Sun’s interior-provided they were detectable. To their dismay, the numbers collected amounted to one-third of what Bahcall had predicted.
One of the key components in the now favoured explanation is that matter behaves differently to anti-matter. He stood by his experiment as others tried to replicate his results or find the problem.
But, while the three experiments may have been conducted around the same time, this week the awards committee only favored McDonald’s and Kajita’s work.
Kajita has been compiling and analyzing data at the Super-Kamiokande neutrino detector, and its predecessor, Kamiokande, located in a deep abandoned mine in the Kamiokacho district of Hida, Gifu Prefecture. Since the Davis detector could only detect one type of neutrino-an electron neutrino, which could cause a nuclear transmutation between chlorine and argon-it seemed possible that the missing neutrinos it hadn’t detected had converted into other neutrino types on their long voyage.
At age 72, Arthur McDonald said winning the Nobel Prize brought him back many years. Neutrinos are so hard to see…
McDonald’s research has focused on neutrinos – a fundamental particle that scientists previously believed held no mass. “They were the last major kind of particle type that was postulated in what we now call the Standard Model”.
Incompleteness is the lifeblood of science. There are still plenty of open questions in neutrino physics that we hope to answer with future experiments.
NICOLE BELL: So the first evidence we’ve had that there are cracks in the Standard Theory, that it’s not the ultimate theory is there really must be something beyond what we know is their existence of neutrino mass.
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Marcelo Gleiser is a theoretical physicist and cosmologist – and professor of natural philosophy, physics and astronomy at Dartmouth College.
