Neutrino Oscillation Physics Potential of the T2K Experiment

Abstract

The observation of the recent electron neutrino appearance in a muon neutrino beam and the high-precision measurement of the mixing angle $\hat{I}{¸}_{13}$ 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 ${\sin }^{2}2\hat{I}{¸}_{23}$, the octant of $\hat{I}{¸}_{23}$, and the mass hierarchy, in addition to the measurements of $\hat{I}{´}_{CP}$, ${\sin }^2\hat{I}{¸}_{23}$, and $\hat{I}”m_{32}^2$, for various combinations of $\hat{I}½$-mode and \(\barν\)-mode data-taking. With an exposure of $7.8\times 10^{21}$~protons-on-target, T2K can achieve 1-$\ddot{I}ƒ$ resolution of 0.050(0.054) on ${\sin }^2\hat{I}{¸}_{23}$ and $0.040(0.045)\times 10^{-3}{\mathrm{eV}}^2$ on $\hat{I}”m_{32}^2$ for 100\%(50\%) neutrino beam mode running assuming ${\sin }^2\hat{I}{¸}_{23}=0.5$ and $\hat{I}”m_{32}^2=2.4\times 10^{-3}$ eV${}^2$. T2K will have sensitivity to the CP-violating phase $\hat{I}{´}_{\mathrm{CP}}$ at 90\% C.L. or better over a significant range. For example, if ${\sin }^{2}2\hat{I}{¸}_{23}$ is maximal (i.e $\hat{I}{¸}_{23}$=$45^{\circ }$) the range is $-115^{\circ }<\hat{I}{´}_{\mathrm{CP}}<-60^{\circ }$ for normal hierarchy and $+50^{\circ }<\hat{I}{´}_{\mathrm{CP}}<+130^{\circ }$ for inverted hierarchy. When T2K data is combined with data from the NO$\hat{I}½$A experiment, the region of oscillation parameter space where there is sensitivity to observe a non-zero $\hat{I}{´}_{CP}$ is substantially increased compared to if each experiment is analyzed alone.

40 pages, 27 figures, accepted by PTEP