New [Formula Presented] violation in neutrino oscillations

Measurements of (Formula presented)-violating observables in neutrino oscillation experiments have been studied in the literature as a way to determine the (Formula presented)-violating phase in the mixing matrix for leptons. Here we show that such observables also probe new neutrino interactions in the production or detection processes. Genuine (Formula presented) violation and fake (Formula presented) violation due to matter effects are sensitive to the imaginary and real parts of new couplings. The dependence of the (Formula presented) asymmetry on the source-detector distance is different from the standard one and, in particular, enhanced at short distances. We estimate that future neutrino factories will be able to probe in this way new interactions that are up to four orders of magnitude weaker than the weak interactions. We discuss the possible implications for models of new physics.