Description
Neutrino oscillation study has entered into the precision era and hence a high precision measurement of $\theta_{23}$ mixing angle is pivotal to address long-standing flavor problem by ruling out different theoritical mass models. The potential of upcoming Deep Underground Neutrino Experiment (DUNE) is highly promising to shed light on the precision of atmospheric oscillation parameters. Current global fit analyses of world oscillation data under 3$\nu$-paradigm give 1.6$\sigma$ indications for lower $\theta_{23}$ octant and prefer normal mass ordering (NMO) at 2.5$\sigma$. In this work, we study in detail the capability of DUNE to resolve $\theta_{23}$ octant at high confidence level in light of present neutrino oscillation data. We observe that DUNE can improve the relative 1$\sigma$ precision in $\sin^2\theta_{23}$ ($\Delta m^2_{23}$) by a factor of 4.4 (2.8) using 3.5 years of $\nu$ and 3.5 years of $\bar{\nu}$ runs, which improves further for 10 years of run-time. We have further shown that, DUNE is more promising in measuring $\Delta m^2_{31}$ with higher precision than upcoming JUNO experiment and synergies of experiments considered in global-fit studies. We have also shown, octant ambiguity of $\theta_{23}$ can be resolved at 3$\sigma$ (5$\sigma$) in DUNE with 336 kt.MW.years exposure if true $\sin^2\theta_{23}\leq0.462(0.450)$ or $\sin^2\theta_{23}\geq0.553(0.569)$ assuming true $\delta_{\mathrm{CP}} =223^\circ$ and true NMO.
