Neutrino oscillation physics potential of the T2K experiment

Abstract

The observation of the recent electron neutrino appearance in a muon neutrino\nbeam and the high-precision measurement of the mixing angle $\\theta_{13}$ have\nled to a re-evaluation of the physics potential of the T2K long-baseline\nneutrino oscillation experiment. Sensitivities are explored for CP violation in\nneutrinos, non-maximal $\\sin^22\\theta_{23}$, the octant of $\\theta_{23}$, and\nthe mass hierarchy, in addition to the measurements of $\\delta_{CP}$,\n$\\sin^2\\theta_{23}$, and $\\Delta m^2_{32}$, for various combinations of\n$\\nu$-mode and \\(\\bar{\\nu}\\)-mode data-taking.\n With an exposure of $7.8\\times10^{21}$~protons-on-target, T2K can achieve\n1-$\\sigma$ resolution of 0.050(0.054) on $\\sin^2\\theta_{23}$ and\n$0.040(0.045)\\times10^{-3}~\\rm{eV}^2$ on $\\Delta m^2_{32}$ for 100\\%(50\\%)\nneutrino beam mode running assuming $\\sin^2\\theta_{23}=0.5$ and $\\Delta\nm^2_{32} = 2.4\\times10^{-3}$ eV$^2$. T2K will have sensitivity to the\nCP-violating phase $\\delta_{\\rm{CP}}$ at 90\\% C.L. or better over a significant\nrange. For example, if $\\sin^22\\theta_{23}$ is maximal (i.e\n$\\theta_{23}$=$45^\\circ$) the range is $-115^\\circ<\\delta_{\\rm{CP}}<-60^\\circ$\nfor normal hierarchy and $+50^\\circ<\\delta_{\\rm{CP}}<+130^\\circ$ for inverted\nhierarchy. When T2K data is combined with data from the NO$\\nu$A experiment,\nthe region of oscillation parameter space where there is sensitivity to observe\na non-zero $\\delta_{CP}$ is substantially increased compared to if each\nexperiment is analyzed alone.\n