2026/08/01 by Tia Pandit, Bipin Singh Koranga, Vivek Kumar Nautiyal
Physics and Astronomy · #hep-ph
18 pages, 6 figures
arxiv created 2026/08/01 · arxiv updated 2026/08/04
We present a unified analysis of two matter-potential systematics in long-baseline (LBL) neutrino oscillation experiments, treating matter-induced extrinsic CPT violation and Earth density stratification as correlated systematics within a single χ2 framework. We study their joint impact on CP-phase reconstruction and mass-ordering dependence. Matter-induced extrinsic CPT violation produces a non-zero asymmetry Aμe\rm CPT=(Pμe- Pμe)/(Pμe+ Pμe), computed using exact three-flavour matrix exponentiation for T2K, NOνA, DUNE, and Hyper-Kamiokande. The asymmetry ranges from 0.022 to 0.180 at the respective peak energies and differs by up to 9% between normal and inverted orderings. The surface Aμe\rm CPT(E,δ\rm CP) at DUNE reveals an interplay between extrinsic CPT and intrinsic CP violation in the high-L/E regime requiring joint statistical treatment. We quantify the sensitivity of Aμe\rm CPT to density uncertainties ρ→ρ(1+ε) with ε=±1%,±2%,±5%, finding that a ±5% uncertainty induces |ΔA\rm CPT|<0.008 at DUNE. Replacing the PREM profile with a constant path-averaged density yields a δ\rm CP reconstruction bias below 0.3^∘ for L≤5000 km, increasing to 17.8^∘ at 7000 km and 172.2^∘ at 12000 km. Since both effects arise from the same matter Hamiltonian, they must be modelled jointly using a Poisson log-likelihood χ2 with nuisance-parameter pulls.