The T2K Experiment

The T2K experiment is designed to study neutrino oscillation. In particular, it is designed to measure the final, previously unmeasured oscillation mixing angle, known as $\theta_{13}$. This mixing angle is responsible for allowing muon neutrinos to oscillate to electron neutrinos. T2K features a nearly pure beam of muon neutrinos, produced at the J-PARC accelerator complex in Tokai, on the East coast of Japan. This beam travels 295 km through the earth, and emerges at the Super-Kamiokande detector, in the mountains in Western Japan, where the neutrinos are detected. At this far detector, the appearance of electron neutrinos from the $\nu_{\mu}$ beam can indicate non-zero $\theta_{13}$. Six electron neutrino candidate events were observed at Super-Kamiokande, with an expected background of 1.5. The probability of observing six or more events from just background is just 0.7\%.