| Abstract: | The observation of the recent electron neutrino appearance in a muon neutrino
beam and the high-precision measurement of the mixing angle $ heta_{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 $sin^22 heta_{23}$, the octant of $ heta_{23}$, and
the mass hierarchy, in addition to the measurements of $delta_{CP}$,
$sin^2 heta_{23}$, and $Delta m^2_{32}$, for various combinations of
$
u$-mode and $ar{
u}$-mode data-taking.
With an exposure of $7.8 imes10^{21}$~protons-on-target, T2K can achieve
1-$sigma$ resolution of 0.050(0.054) on $sin^2 heta_{23}$ and
$0.040(0.045) imes10^{-3}~
m{eV}^2$ on $Delta m^2_{32}$ for 100%(50%)
neutrino beam mode running assuming $sin^2 heta_{23}=0.5$ and $Delta
m^2_{32} = 2.4 imes10^{-3}$ eV$^2$. T2K will have sensitivity to the
CP-violating phase $delta_{
m{CP}}$ at 90% C.L. or better over a significant
range. For example, if $sin^22 heta_{23}$ is maximal (i.e
$ heta_{23}$=$45^circ$) the range is $-115^circ<delta_{
m{CP}}<-60^circ$
for normal hierarchy and $+50^circ<delta_{
m{CP}}<+130^circ$ for inverted
hierarchy. When T2K data is combined with data from the NO$
u$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. |
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