Interplay of CPT-Violating and CPT-Conserving Lorentz Invariance Violation at DUNE

Abstract

We present a study of Lorentz invariance violation (LIV) in neutrino oscillations, with primary emphasis on the interplay between CPT-violating and CPT-conserving Standard Model Extension (SME) coefficients. We find that $a_{ee}$ and $a_{ττ}$ dominate among the diagonal LIV coefficients, whereas $a_{eμ}$ and $a_{eτ}$ provide the most significant off-diagonal contributions. In contrast, the corresponding $c_{αβ}$ coefficients have comparatively sub-leading effects. Taking DUNE as a representative long-baseline experiment, we show that the sensitivity to CP violation is modified by LIV in a parameter-specific manner. We find correlations between off-diagonal LIV parameters, and non-trivial dependence on the new phases. In absence of LIV, DUNE is expected to establish CP violation at $5σ$ for a limited fraction of $δ_{CP}$ values. We find that the presence of $a_{ee}$, $a_{ττ}$, $a_{eμ}$ and $a_{eτ}$ weakens the CP discovery potential, reducing the achievable significance to below $3σ$ over a substantial fraction of $δ_{\rm CP}$. The independent impact of $c_{αβ}$ terms also results in suppression, but in combination with $a_{αβ}$, they introduce degeneracies, complicating the extraction of $δ_{CP}$. This generally results in a deterioration of CP violation sensitivities below $5σ$. These findings emphasize the importance of incorporating LIV effects in precision oscillation studies at upcoming long-baseline experiments.