  The observation of the recent electron neutrino appearance in a muon neutrino
beam and the high-precision measurement of the mixing angle $\theta_{13}$ 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 $\sin^22\theta_{23}$, the octant of $\theta_{23}$, and
the mass hierarchy, in addition to the measurements of $\delta_{CP}$,
$\sin^2\theta_{23}$, and $\Delta m^2_{32}$, for various combinations of
$\nu$-mode and \(\bar{\nu}\)-mode data-taking.
  With an exposure of $7.8\times10^{21}$~protons-on-target, T2K can achieve
1-$\sigma$ resolution of 0.050(0.054) on $\sin^2\theta_{23}$ and
$0.040(0.045)\times10^{-3}~\rm{eV}^2$ on $\Delta m^2_{32}$ for 100\%(50\%)
neutrino beam mode running assuming $\sin^2\theta_{23}=0.5$ and $\Delta
m^2_{32} = 2.4\times10^{-3}$ eV$^2$. T2K will have sensitivity to the
CP-violating phase $\delta_{\rm{CP}}$ at 90\% C.L. or better over a significant
range. For example, if $\sin^22\theta_{23}$ is maximal (i.e
$\theta_{23}$=$45^\circ$) the range is $-115^\circ<\delta_{\rm{CP}}<-60^\circ$
for normal hierarchy and $+50^\circ<\delta_{\rm{CP}}<+130^\circ$ for inverted
hierarchy. When T2K data is combined with data from the NO$\nu$A experiment,
the region of oscillation parameter space where there is sensitivity to observe
a non-zero $\delta_{CP}$ is substantially increased compared to if each
experiment is analyzed alone.
