Neutrino Nobel Puts scientists on Cloud Nine

The breakthrough has shaken the previous Standard Model of particle physics and a decades-old physics puzzle. Interestingly, there are many heavy cousins of familiar particles that exist only for fractions of a second, and thus are not part of ordinary matter. Lindley Winslow aims her research at understanding the nature of neutrino mass; in particular, whether neutrinos might be their own anti-particle. They are everywhere. About 65 billion neutrinos, produced by nuclear fusion in the Sun, pass through every square centimetre of area on Earth, every second (you could try and calculate that yourself), without doing anything.

The University of Tokyo said in a statement congratulating Kajita that he was one of the students of 2002 Nobel physics victor Masatoshi Koshiba, who also has contributed to Japan’s neutrino research. What they found out was that the neutrino is even more interesting than we thought. The 2015 prize was awarded to Takaaki Kajita of the Super-Kamiokande Experiment and Arthur McDonald of the Sudbury Neutrino Observatory (SNO) “for the discovery of neutrino oscillations, which shows that neutrinos have mass”.

It turns out that for neutrinos of 1 GeV and lower, Earth’s atmosphere is just high enough to allow neutrinos to oscillate. According to the Standard Model of particle physics there are three types of neutrinos – electron-neutrinos, muon-neutrinos and tau-neutrinos. Clearly this was ground-breaking news. However, as always, these new insights led to further questions. To understand the phenomenon in greater detail, physicists are now generating beams of neutrinos at many sites over the world, including Fermilab, Brookhaven, CERN and the KEK laboratory in Japan.

As was the case with the solar neutrino problem, measuring a deficit in the expected number of neutrinos does not by itself constitute proof that neutrinos oscillate. All particles have anti-particles.

The story of neutrino oscillations involves not just particle physics, but also nuclear physics and astrophysics. In fact it could be virtually the same, but still behave differently. Shortly after the Big Bang, the universe was filled with a hot soup of energy and matter. What we learn about the matter/antimatter asymmetry could change our very understanding of how the universe evolved to the present day. Not really, all the matter would be gone as well. But the difference between how neutrinos and anti-neutrinos change the colour of their jacket isn’t going to provide the entire solution. This transformation can only come about if neutrinos are “massive” (albeit with a very tiny mass). And we still have much more to learn about neutrinos. Measuring their mass and a few other properties is harder still. Wolfgang Pauli proposed the existence of a new neutral particle in 1930 to preserve the conservation of energy, momentum, and spin in beta decay. Oscillation between flavors is the result of the different mass eigenstates evolving at different rates. My group is pursuing novel ways to determine the mass scale of neutrinos and their impact on our understanding of cosmology.

“We do not know how to make predictions about how neutrinos will behave”, Klein said.

McDonald explained that while he was director of Sudbury Neutrino Observatory Institute on neutrinos from the Sun, he had noticed large numbers of neutrinos from the Sun that were very hard to detect. “Neutrinos could give a clue regarding this”, said Mondal. Yet in our current universe, we see only matter. Which one of them is lightest or heaviest? (Why so deep? So that the rock would block other particles, leaving mostly neutrinos to be detected.) Bahcall had calculated the number of neutrinos that the sun should be producing and sending our direction as it fused hydrogen into helium at its core.