T2K is a neutrino experiment designed to investigate how neutrinos change from one flavour to another as they travel (neutrino oscillations). An intense beam of muon neutrinos is generated at the J-PARC nuclear physics site on the East coast of Japan and directed across the country to the Super-Kamiokande neutrino detector in the mountains of western Japan. The beam is measured once before it leaves the J-PARC site, using the near detector ND280, and again at Super-K: the change in the measured intensity and composition of the beam is used to provide information on the properties of neutrinos.

Science Goals of T2K

• the discovery of ν_μ → ν_e ( i.e. the confirmation that θ₁₃ > 0 )
• precision measurements of oscillation parameters in ν_μ disappearance
• a search for sterile components in ν_μ disappearance by observation of neutral-current events
• world-leading contributions to neutrino-nucleus cross-section measurements

Of all the known particles in the Standard Model (excluding the still-undiscovered Higgs boson), neutrinos are the least well understood. Almost massless, and so reluctant to interact with other particles that they can travel right through the Earth without even noticing, neutrinos are among the most difficult particles to study in experiments. Yet they are crucial to the world as we know it: the nuclear reactions that make the Sun shine and create most of the elements of the Periodic Tableinvolve neutrinos, and they may even explain why our universe is made of matter and not antimatter.

Find out more about these mysterious and elusive particles with our guide to neutrinos: the Neutrino FAQ, for those who are new to the subject, and our detailed guide for the more knowledgeable and/or adventurous.