Anisotropic Lorentz invariance violation in reactor neutrino experiments

Abstract

Recent reactor neutrino oscillation experiments reported precision measurements of $\sin^2 2\theta_{13}$ and $\Delta m^2_{ee}$ under the standard 3$\nu$ oscillation framework. However, inter-experiment consistency checks through the parameter goodness-of-fit test reveal proximity to the tension boundary, with the Double Chooz, RENO, and Daya Bay ensemble yielding $p_\text{PG}=0.14$ vs threshold $\alpha=0.1$. Anisotropic Lorentz invariance violation (LIV) can accommodate this tension by introducing a location-dependent angle $\theta^\text{LIV}$ relative to the earth's axis. It is found that anisotropic LIV improve the fit to data up to 1.9$\sigma$ confidence level significance, with the coefficient $\mathcal{A}^{C(0)}_{31} = 2.43\times 10^{-17}\text{ MeV}$ yielding the best fit, while Parameter Goodness-of-fit (PG) is significantly improved within the LIV formalism.