The Nobel Prize in Physics for 2015 and UnivEarthS

The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics for 2015 to Takaaki Kajita and Arthur B. McDonald “for the discovery of neutrino oscillations, which shows that neutrinos have mass”
Neutrinos are elementary particles, present everywhere in large quantities, and have played an important role in the evolution of the Universe. They are very elusive, but physicists have suceed to trap them and to study their properties. There are three families, which we call “flavors”, and they have the strange property of manifest sometimes in our detectors with a different flavor from the one they had at their birth.

It was in 1998 that this strange property, also called “oscillation” was confirmed when Takaaki Kajita, director of the Institute for Research on cosmic rays, discovered that neutrinos from the atmosphere “changed their identities” on their way to the Super-Kamiokande detector in Japan. At the same time, the research group led by Arthur B. McDonald, emeritus professor at Queen’s University in Canada, demonstrated that neutrinos from the Sun did not disappear on their way to Earth; they were captured with a different identity on arrival at the Sudbury Neutrino Observatory.

In 2015, it is already the fourth time that research on neutrinos are distinguished by the Nobel committee. According to the Swedish jury, this discovery “changed our understanding of the innermost workings of matter and can be crucial to our vision of the universe. ”

Neutrinos are now so well known that LabEx UnivEarthS teams use them to study the internal structure of the Earth: the neutrinos produced in the mantle and crustal give us informations about the materials they contain, while neutrinos produced in atmosphere and which crossed the Earth can carry information on the composition of the heart. Obviously, it is essential for these studies to know and consider the oscillations of neutrinos.

Some links to go further:

– The Interface “Geophysics” Labex project, which aims to develop methods of auscultation of the Earth using particles (neutrinos, muons)

– The Borexino detector at the Gran Sasso National Laboratory in Italy, which measured neutrinos from Earth:

– The DUNE experience, to be built in the US, can accurately measure the neutrinos generated in the atmosphere by cosmic rays: