Detecting CP Violation in the Presence of Non-Standard Neutrino Interactions

New physics beyond the Standard Model could appear at long baseline oscillation experiments as non-standard interactions (NSI) between neutrinos and matter. This would make determination of the CP-violating phase δ₁₃ ambiguous due to interference with additional complex phases in the mixing matrix. In this talk I'll show how the CP phase degeneracies are visualized on biprobability plots, and how degeneracies and their breaking can be understood based on a perturbative expansion. I'll apply this to experimental hints that suggest δ₁₃ ∼ -π/2, which could also be consistent with δ₁₃, δ_eτ = 0, π for large ε_eτ, and I'll show how both the longer baseline and broader energy spectrum of DUNE can help distinguish these cases.