T2K (Tokai-to-Kamioka) is a long-baseline neutrino oscillation experiment in which a neutrino beam produced by using the accelerator facility at J-PARC (Japan Proton Accelerator Research Center) is sent 295 km across Japan to the Super-Kamiokande (SK)  detector. The energy of the beam is tuned to peak at 600 MeV using the "off-axis" technique, whereby the beam is directed 2.5 degrees away from the SK detector; at this energy, the neutrino oscillation probability is expected to be maximum for the distance of 295 km.

The experiment started operations in 2010 and has accumulated a significant amount of data with both a muon neutrino and muon antineutrino beam.

The T2K experiment has achieved a few major milestones in the study of neutrino oscillations including:

• The first observation of muon neutrino to electron neutrino oscillation, which was also the first time neutrinos produced in one flavor were seen explicitly interacting as neutrinos of a different flavor.
• The most precise measurements of the mixing parameter θ23 through muon neutrino disappearance
• Through a combination of neutrino and antineutrino oscillation measurements, T2K may be seeing the first hints of CP violation, an asymmetry in the oscillation probability between the muon neutrino to electron neutrino oscillation and its antineutrino counterpart.

SLAC activites on T2K include:

• Development of new reconstruction algorithms for the Super-Kamiokande detector to enhance the identification of electron neutrino events crtiical for the CP violation search
• Improvements to the primary proton beam monitoring to accommodate the large increase in beam power expected at J-PARC in the next few years.