Measurements of neutrino oscillation in appearance and disappearance channels by the T2K experiment with 6.6 × 10²⁰protons on target

We report on measurements of neutrino oscillation using data from the T2K long-baseline neutrino experiment collected between 2010 and 2013. In an analysis of muon neutrino disappearance alone, we find the following estimates and 68% confidence intervals for the two possible mass hierarchies: normal hierarchy: sin²θ₂₃= 0.514_-0.056 ^+0.055and Δm₃₂ ²= (2.51 ± 0.10) × 10^-3eV²/c⁴and inverted hierarchy: sin²θ₂₃= 0.511 ± 0.055 and Δm₁₃ ²= (2.48 ± 0.10) × 10^-3eV²/c⁴. The analysis accounts for multinucleon mechanisms in neutrino interactions which were found to introduce negligible bias. We describe our first analyses that combine measurements of muon neutrino disappearance and electron neutrino appearance to estimate four oscillation parameters, |Δm²|, sin²θ₂₃, sin²θ₁₃, δ_CP, and the mass hierarchy. Frequentist and Bayesian intervals are presented for combinations of these parameters, with and without including recent reactor measurements. At 90% confidence level and including reactor measurements, we exclude the region δ_CP= [0.15; 0.83]π for normal hierarchy and δ_CP= [-0.08; 1.09]π for inverted hierarchy. The T2K and reactor data weakly favor the normal hierarchy with a Bayes factor of 2.2. The most probable values and 68% one-dimensional credible intervals for the other oscillation parameters, when reactor data are included, are sin²θ₂₃= 0.528_-0.038 ^+0.055and |Δm₃₂ ²| = (2.51 ± 0.11) × 10^-3eV²/c⁴.