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 \(\theta_{13}\) 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.