Preliminary results of MINOS experiment indicate that theta23 is not maximal.
Global fits to world neutrino data suggest two nearly degenerate solutions for
theta23: one in the lower octant (LO: theta23 < 45 degree) and the other in the
higher octant (HO: theta23 > 45 degree). numu to nue oscillations in superbeam
experiments are sensitive to the octant and are capable of resolving this
degeneracy. We study the prospects of this resolution by the current T2K and
upcoming NOvA experiments. Because of the hierarchy-deltacp degeneracy and the
octant-deltacp degeneracy, the impact of hierarchy on octant resolution has to
be taken into account. As in the case of hierarchy determination, there exist
favorable (unfavorable) values of deltacp for which octant resolution is easy
(challenging). However, for octant resolution the unfavorable deltacp values of
the neutrino data are favorable for the anti-neutrino data and vice-verse. This
is in contrast to the case of hierarchy determination. In this paper, we
compute the combined sensitivity of T2K and NOvA to resolve the octant
ambiguity. If sin^2\theta23 =0.41, then NOvA can rule out all the values of
theta23 in HO at 2 sigma C.L., irrespective of the hierarchy and deltacp.
Addition of T2K data improves the octant sensitivity. If T2K were to have equal
neutrino and anti-neutrino runs of 2.5 years each, a 2 sigma resolution of the
octant becomes possible provided sin^2\theta23 \leq 0.43 or \geq 0.58 for any
value of deltacp.Comment: 27 pages, 38 pdf figures, 1 table. New figures are given in the
results section to show the octant discovery reach as a function of true
theta23 and true CP phase. Few changes in the abstract, results and
conclusions section to incorporate the new results. Published in JHE
