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: $\sin^2\theta_{23}=0.514^{+0.055}_{-0.056}$ and $\Delta
m^2_{32}=(2.51\pm0.10)\times 10^{-3}$ eV$^2$/c$^4$
Inverted Hierarchy: $\sin^2\theta_{23}=0.511\pm0.055$ and $\Delta
m^2_{13}=(2.48\pm0.10)\times 10^{-3}$ eV$^2$/c$^4$
The analysis accounts for multi-nucleon 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 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:
$\delta_{CP}=[0.15,0.83]\pi$ for normal hierarchy and
$\delta_{CP}=[-0.08,1.09]\pi$ 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% 1D credible intervals for the
other oscillation parameters, when reactor data are included, are:
$\sin^2\theta_{23}=0.528^{+0.055}_{-0.038}$ and $|\Delta
m^2_{32}|=(2.51\pm0.11)\times 10^{-3}$ eV$^2$/c$^4$.