Can Lorentz Invariance Violation affect the Sensitivity of Deep Underground Neutrino Experiment?

TL;DR

This paper investigates how Lorentz Invariance Violation (LIV) could impact the ability of the DUNE experiment to determine neutrino oscillation parameters, revealing potential degeneracies and conditions for maintaining sensitivity.

Contribution

It introduces the effects of CPT-violating LIV parameters on neutrino oscillation measurements and analyzes their influence on DUNE's sensitivity to the octant of b2_{23} and CP phases.

Findings

LIV can significantly deteriorate DUNE's octant resolution for certain parameter values.

When both LIV parameters are present, their effects can cancel, improving sensitivity.

CP phases can be reconstructed with 10-15b0 uncertainty for b4 and 25-30b0 for LIV phases.

Abstract

We examine the impact of Lorentz Invariance Violation (LIV) in measuring the octant of $\theta_{23}$ and CP phases in the context of the Deep Underground Neutrino Experiment (DUNE). We consider the CPT-violating LIV parameters involving $e - \mu$ ($a_{e\mu}$) and $e - \tau$ ($a_{e\tau}$) flavors, which induce an additional interference term in neutrino and antineutrino appearance probabilities. This new interference term depends on both the standard CP phase $\delta$ and the new dynamical CP phase $\varphi_{e\mu}$/$\varphi_{e\tau}$, giving rise to new degeneracies among ($\theta_{23}$, $\delta$, $\varphi$). Taking one LIV parameter at-a-time and considering a small value of $|a_{e\mu}| = |a_{e\tau}| = 5 \times 10^{-24}$ GeV, we find that the octant discovery potential of DUNE gets substantially deteriorated for unfavorable combinations of $\delta$ and $\varphi_{e\mu}$/$\varphi_{e\tau}$. The octant of $\theta_{23}$ can only be resolved at $3\sigma$ if the true value of $\sin^2\theta_{23} \lesssim 0.42$ or $\gtrsim 0.62$ for any choices of $\delta$ and $\varphi$. Interestingly, we also observe that when both the LIV parameters $a_{e\mu}$ and $a_{e\tau}$ are present together, they cancel out the impact of each other to a significant extent, allowing DUNE to largely regain its octant resolution capability. We also reconstruct the CP phases $\delta$ and $\varphi_{e\mu}$/$\varphi_{e\tau}$. The typical $1\sigma$ uncertainty on $\delta$ is $10^{\circ}$ to $15^{\circ}$ and the same on $\varphi_{e\mu}$/$\varphi_{e\tau}$ is $25^{\circ}$ to $30^{\circ}$ depending on the choices of their true values.