European Physical Journal C: Particles and Fields (Apr 2020)
Long baseline neutrino oscillation experiments with accelerators in Japan
Abstract
Abstract The development of long baseline neutrino oscillation experiments with accelerators in Japan is reviewed. Accelerator experiments can optimize experimental conditions, such as the beam and the detector, as needed. The evidence of neutrino oscillations observed in atmospheric neutrinos was confirmed by the K2K experiment. The T2K experiment discovered the oscillation channel from a muon neutrino to an electron neutrino with the squared mass difference $$\varDelta m^2 \sim 2.5 \times 10^{-3}~\mathrm{eV}^2$$ Δm2∼2.5×10-3eV2 , and presents a full analysis with all three flavor states of both neutrinos and anti-neutrinos. The three mixing angles, which quantify the mixing of the three neutrino states, have been measured. They are large compared to those of quarks, especially the mixing of the second and third generation which is nearly maximal. The T2K experiment has an ongoing program producing new results, and recently has shown a hint of CP violation in neutrinos. Future generation long baseline neutrino experiments beyond T2K are expected to clarify the relationship between flavor and mass, as well as measure possible CP violation in neutrino oscillations.