Octant of $\theta_{23}$ at long baseline neutrino experiments in the light of Non Unitary Leptonic mixing

TL;DR

This paper investigates how non-unitarity in the leptonic mixing matrix affects the ability of long-baseline neutrino experiments to determine the octant of the atmospheric mixing angle $ heta_{23}$, revealing potential limitations in their sensitivity.

Contribution

It provides a detailed analysis of octant degeneracy considering non-unitarity effects, highlighting the impact on experimental sensitivity and discovery potential.

Findings

Non-unitarity hampers octant determination in neutrino experiments.

Octant sensitivity is reduced in the presence of non-unitarity.

Experiments' capability to resolve the octant is compromised by non-unitarity.

Abstract

The octant of the atmospheric mixing angle $\theta_{23}$ is still undetermined by neutrino oscillation experiments. Long-baseline experiments like NO$\nu$A, T2K and DUNE offer good prospects for determining the octant of $\theta_{23}$. However, their capability to do so may be compromised by the possible presence of non-unitarity in the leptonic mixing matrix. In this paper, we study in detail the octant degeneracy with and without non-unitarity at the level of oscillation probabilities and events for these experiments. We also analyze their octant sensitivity and discovery reach and show that they are hampered in the presence of non-unitarity.