Nobel prize 2015

08/10/2015
The Super-Kamiokande neutrino detector Super-K

The Nobel price committee honored the Japanese neutrino physicist Takaaki Kajita and his Canadian colleague Arthur McDonald for first detection of transitions between different types of neutrinos. Our institute congratulates the laureates! We are particularly happy about the award for Kajita to whom we have a direct connection: we are collaborating with him on the T2K project.

But let’s start at the beginning. In 1996 the Super-Kamiokande detector on Japan’s west coast started operation. Two years later Kajita managed to show, that muon-neutrinos created by the impact of cosmic rays on the earth’s atmosphere disappear on their path to the Super-Kamiokande detector. Now he is awarded for this achievement. Today we understand that the neutrinos don’t disappear, but they transform into tau-neutrinos which cannot be detected in Super-Kamiokande. Soon after an idea was shaped to extend the project with an artificial beam of myon-neutrinos. The beam will be created at the Japanese research center JPARC (Japanese Proton Accelerator Research Complex) on the Japanese east coast near the city of Tokai. Around 2005 construction started. Since 2006 our institute is collaborating with Kajita on this project. The project is called T2K for Tokai-to-Kamioka. Our involvement is led by Stefan Roth. His topic is the research on the Time Projection Chambers (TPC) of the near detector ND280 at JPARC. At inspects the beam before it is send 295 km through the earth to the Super-Kamiokande detector. He developed with his group a system of monitoring chambers. They are continuously checking and calibrating the TPCs. The chambers are installed on-site at JPARC. The data is analyzed in Aachen and the results are fed back into the experiment’s data base in Japan.

T2K near detector T2K

In 2011 T2K had its first success. Kajita had discovered the transition from myon- to tau-neutrinos with Super-Kamiokande and McDonald had shown that electron-neutrinos convert into myon-neutrinos. Finally T2K managed to demonstrate the third transition possible, from electron-neutrinos to tau-neutrinos. Shortly after we were able to confirm this finding with our DoubleChooz project. Meanwhile T2K switched the beam from neutrinos to antineutrinos, pursuing the question whether there are any differences between the behavior of neutrinos and antineutrinos and whether this might give a hint on the disappearance of the antimatter from the evolution of our universe.

Finally we want to mention that also our IceCube project at the south pole observes since a few years the same transition that led to Kajita’s award. Neutrino oscillations are a focus of research at our institute. We are particularly happy about the Nobel prices for Kajita and McDonald.