Sanjib Kumar Agarwalla, Suprabh Prakash, S. Uma Sankar
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 < pi/4) and the other in the higher octant (HO: theta23 > pi/4). 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 LO is the true octant, then NOvA can rule out HO at 2sigma C.L., irrespective of the hierarchy and deltacp. Addition of T2K data improves the octant sensitivity. If HO and normal hierarchy are the true choices, then the combined data from NOvA and T2K with its designed five years run in neutrino mode, is incapable of a 2sigma resolution of the octant for all deltacp. A 2sigma resolution of the octant, for all combinations of neutrino parameters, becomes possible if T2K has balanced neutrino and anti-neutrino runs of 2.5 years each.
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http://arxiv.org/abs/1301.2574
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