Speaker
Description
The precision determination of the leptonic CP-violating phase $\delta_{CP}$ is one of the main goals of the upcoming long-baseline experiments DUNE and Hyper-Kamiokande. Within the standard three-flavor framework and the usual assumptions on neutrino cross sections -- namely lepton universality and accurate nuclear modeling -- both experiments are projected to reach high sensitivity to $\delta_{CP}$.
In this talk I examine how robust this picture really is. First, I show that a model-agnostic, data-driven treatment of current cross-section data allows smooth deformations of $\sigma_{\nu_e}$ that degrade the CP sensitivity by 3--4$\sigma$ at maximal CP violation, exposing how much of the projected reach is rooted in theoretical assumptions rather than in measurements. Second, I show that even if these assumptions hold, any unmodeled new physics in neutrino propagation -- illustrated by the NSI solutions to the present NOνA–T2K tension -- affects DUNE and Hyper-Kamiokande differently due to their distinct matter effects, generating an artificial tension at the $\sim 3\sigma$ level between their inferred parameters. Taken together, these results suggest that, in the precision era, tensions between long-baseline experiments may themselves serve as a diagnostic tool, pointing either to hidden systematics or to physics beyond the Standard Model.
