Neutrino oscillation physics potential of the T2K experiment

The observation of the recent electron neutrino appearance in a muon neutrino beam and the high-precision measurement of the mixing angle Θ₁₃ have led to a re-evaluation of the physics potential of the T2K long-baseline neutrino oscillation experiment. Sensitivities are explored for CP violation in neutrinos, non-maximal sin² 2Θ₂₃, the octant of Θ₂₃, and the mass hierarchy, in addition to the measurements of δ_CP, sin² Θ₂₃, and Δm² ₃₂, for various combinations of ν-mode and ν-mode data-taking. With an exposure of 7.8 × 10²¹ protons-on-target, T2K can achieve 1 σ resolution of 0.050 (0.054) on sin² Θ₂₃ and 0.040 (0.045) × 10^-3 eV² on Δm² ₃₂ for 100% (50%) neutrino beam mode running assuming sin² Θ₂₃ = 0.5 and Δm² ₃₂ = 2.4 × 10^-3 eV². T2K will have sensitivity to the CP-violating phase δ_CP at 90% C.L. or better over a significant range. For example, if sin² 2Θ₂₃ is maximal (i.e. Θ₂₃ = 45°) the range is -115° < δ_CP < -60° for normal hierarchy and +50° < δ_CP < +130° for inverted hierarchy. When T2K data is combined with data from the NOνA experiment, the region of oscillation parameter space where there is sensitivity to observe a non-zero δ_CP is substantially increased compared to if each experiment is analyzed alone.