The following text is from a press release issued by the Japanese high-energy physics laboratory KEK earlier today.
Physicists from the Japanese-led multi-national T2K neutrino collaboration announced today that over the weekend they detected the first events generated by their newly built neutrino beam at the J-PARC accelerator laboratory in Tokai, Japan. Protons from the 30-GeV Main Ring synchrotron were directed onto a carbon target, where their collisions produced charged particles called pions. These pions travelled through a helium-filled volume where they decayed to produce a beam of the elusive particles called neutrinos. These neutrinos then flew 200 metres through the earth to a sophisticated detector system capable of making detailed measurements of their energy, direction, and type.
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The data from the complex detector system is still be analysed, but the physicists have seen at least 3 neutrino events, in line with the expectation based on the current beam and detector performance. Prof. Koichiro Nishikawa, director of the Institute for Particle and Nuclear physics at the KEK laboratory and founder of the T2K collaboration, said "The T2K experiment is about to reveal another mystery of neutrinos. I would like to thank everyone who has been supporting this experiment directly or indirectly and to thank our excellent collaborators from all over the world for making it possible to reach this stage of the experiment. All the people in T2K also owe a big debt to the accelerator physicists who worked so hard to build and commission the accelerators. And especially, I would like to thank Japanese government and all of the foreign governments for giving us a strong support and I would like to ask for continuing support. We are ready to do our best to reveal the full mysteries of neutrinos."
This detection marks the beginning of the operational phase of the T2K experiment, a ~500 physicist, 12 nation collaboration to measure new properties of the ghostly neutrino. Prof. Atsuto Suzuki, Director General of the KEK laboratory, said "Studies of neutrinos in the T2K experiment are going to unveil unknown properties of neutrinos. Researchers around the world must be jealous that once again neutrinos seem to like to reveal new properties in Japan! Neutrino detection is the first step toward it and I can hardly wait to see the experimental results."
Neutrinos interact only weakly with matter, and thus pass effortlessly through the earth (and mostly through the detectors!). Neutrinos exist in three types, called electron, muon, and tau; linked by particle interactions to their more familiar charged cousins like the electron. Measurements over the last few decades, notably by the Super-Kamiokande and KamLAND neutrino experiments in western Japan, have shown that neutrinos possess the strange property of neutrino oscillations, whereby one type of neutrino will turn into another as they propagate through space. Neutrino oscillations, which require neutrinos to have mass and therefore were not allowed in our previous theoretical understanding of particle physics, probe new physical laws and are thus of great interest in the study of the fundamental constituents of matter. They may even be related to the mystery of why there is more matter than anti-matter in the universe, and thus are the focus of intense study worldwide.
Dr. Takashi Kobayashi, Spokesperson of the T2K experiment, said "The study of neutrino oscillations is one of our best keys for really understanding the most fundamental laws of physics, and this weekend's progress brings us one more step towards fully understanding them."
Read more in the full press release.