Determination of the $��_{23}$ octant in long baseline neutrino experiments within and beyond the standard model

The recent data indicate that the neutrino mixing angle $��_{23}$ deviates from the maximal-mixing value of 45$^\circ$, showing two nearly degenerate solutions, one in the lower octant (LO) ($��_{23}45^\circ$). We investigate, using numerical simulations, the prospects for determining the octant of $��_{23}$ in the future long baseline oscillation experiments. We present our results as contour plots on the ($��_{23}-45^\circ$, $��$)--plane, where $��$ is the $CP$ phase, showing the true values of $��_{23}$ for which the octant can be experimentally determined at 3$\,��$, 2$\,��$ and 1$\,��$ confidence level. In particular, we study the impact of the possible nonunitarity of neutrino mixing on the experimental determination of $��_{23}$ in those experiments.
17 pages, 5 figures