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

A bstract Recent global fit analyses of 3 ν oscillation data show a preference for normal mass ordering (NMO) at 2.5 σ and provide 1.6 σ indications for lower θ 23 octant (sin 2 θ 23 < 0 . 5) and leptonic CP violation (sin δ CP < 0). In this work, we study in detail the capabilities of DUNE to establish the deviation from maximal θ 23 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 ν ¯ disappearance events, we discuss the impact of sin 2 θ 23 – ∆ m 31 2 degeneracy in establishing non-maximal θ 23 and show how this degeneracy can be resolved with the help of spectral analysis. A 3 σ (5 σ ) determination of non-maximal θ 23 is possible in DUNE with an exposure of 336 kt · MW · years if the true value of sin 2 θ 23 ≲ 0 . 465 (0 . 450) or sin 2 θ 23 ≳ 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 θ 23 . We observe that both ν and ν ¯ data are essential to settle the θ 23 octant at a high confidence level. DUNE can resolve the octant of θ 23 at 4.2 σ (5 σ ) using 336 (480) kt · MW · years of exposure for the present best-fit values of oscillation parameters. DUNE can improve the current relative 1 σ precision on sin 2 θ 23 (∆ m 31 2 ) by a factor of 4.4 (2.8) using 336 kt · MW · years of exposure.