A close look on 2-3 mixing angle with DUNE in light of current neutrino oscillation data

Abstract

Recent global fit analyses of 3ν oscillation data show a preference for normal mass ordering (NMO) at 2.5σ and provide 1.6σ indications for lower θ23 octant (sin2θ23< 0.5) and leptonic CP violation (sin δCP< 0). In this work, we study in detail the capabilities of DUNE to establish the deviation from maximal θ23 and to resolve its octant in light of the current data. Introducing for the first time, a bi-events plot in the plane of total ν and overline{nu} disappearance events, we discuss the impact of sin2θ23 – ∆ {m}_{31}^2 degeneracy in establishing non-maximal θ23 and show how this degeneracy can be resolved with the help of spectral analysis. A 3σ (5σ) determination of non-maximal θ23 is possible in DUNE with an exposure of 336 kt·MW·years if the true value of sin2θ23 ≲ 0.465 (0.450) or sin2θ23 ≳ 0.554 (0.572). We study the role of appearance and disappearance channels, systematic uncertainties, marginalization over oscillation parameters, and the importance of spectral analysis in establishing non-maximal θ23. We observe that both ν and overline{nu} data are essential to settle the θ23 octant at a high confidence level. DUNE can resolve the octant of θ23 at 4.2σ (5σ) using 336 (480) kt·MW·years of exposure for the present best-fit values of oscillation parameters. DUNE can improve the current relative 1σ precision on sin2θ23 (∆ {m}_{31}^2 ) by a factor of 4.4 (2.8) using 336 kt·MW·years of exposure.