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Resolving the octant of θ 23 with T2K and NOνA

  • Sanjib Kumar Agarwalla
  • Suprabh Prakash
  • S. Uma Sankar
Article

Abstract

Preliminary results of MINOS experiment indicate that θ 23 is not maximal. Global fits to world neutrino data suggest two nearly degenerate solutions for θ 23: one in the lower octant (LO: θ 23 < 45) and the other in the higher octant (HO: θ 23 > 45). ν μ → ν e 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 NOνA experiments. Because of the hierarchy-δ CP degeneracy and the octant-δ CP 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 δ CP for which octant resolution is easy (challenging). However, for octant resolution the unfavorable δ CP 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 NOνA to resolve the octant ambiguity. If sin2 θ 23 = 0.41, then NOνA can rule out all the values of θ 23 in HO at 2σ C.L., irrespective of the hierarchy and δ CP. 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 2σ resolution of the octant becomes possible provided sin2 θ 23 ≤ 0.43 or ≥ 0.58 for any value of δ CP.

Keywords

Neutrino Physics CP violation Beyond Standard Model 

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Copyright information

© SISSA, Trieste, Italy 2013

Authors and Affiliations

  • Sanjib Kumar Agarwalla
    • 1
    • 2
  • Suprabh Prakash
    • 3
  • S. Uma Sankar
    • 3
  1. 1.Institute of Physics, Sachivalaya Marg, Sainik School PostBhubaneswarIndia
  2. 2.Instituto de Física CorpuscularCSIC-Universitat de ValènciaValenciaSpain
  3. 3.Department of Physics, Indian Institute of Technology BombayMumbaiIndia

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