Octant Ambiguity in the Presence of Non-isotropic Lorentz Invariance Violation

TL;DR

This paper investigates how non-isotropic Lorentz violation impacts the measurement of the neutrino mixing angle 23, revealing that it hampers resolving the octant ambiguity and increases degeneracy with the CP-phase in future experiments.

Contribution

First analysis of non-isotropic Lorentz violation effects on 23 measurements, highlighting challenges for resolving the octant ambiguity in neutrino experiments.

Findings

Lorentz violation parameter c^{xy}_{e au} impairs DUNE's ability to resolve 23 octant ambiguity.

Lorentz invariance violation increases degeneracy between 23 and cp.

Sidereal effects significantly influence neutrino oscillation measurements.

Abstract

Global analyses of neutrino data suggest that the mixing angle $\theta_{23}$ is likely to be nonmaximal with two closely matched solutions emerging: one representing a smaller angle ($\theta_{23}$ < $\pi/4$) and the other a larger angle ($\theta_{23}$ > $\pi/4$). This ambiguity, known as the octant ambiguity of $\theta_{23}$, presents a significant challenge in neutrino research and is a primary objective of future long-baseline experiments. In this study, for the first time, we explore how non-isotropic Lorentz violation affects measurements of mixing angle $\theta_{23}$, with a particular emphasis on sidereal effects in the Deep Underground Neutrino Experiment. Our findings reveal that ability of DUNE to resolve the octant ambiguity is significantly compromised in the presence of the $c^{xy}_{e \tau}$ parameter. Furthermore, we demonstrate that LIV exacerbates the degeneracy between the Dirac CP-phase $\delta_{cp}$ and $\theta_{23}$.