Towards Measuring the CP-Violating Phase with Atmospheric Neutrinos

We propose a new approach to measure the CP-violating phase in neutrino mixing using atmospheric neutrinos, improving upon prior work. Because it is subject to systematic uncertainties that differ from those affecting accelerator-based measurements, the two approaches are complementary, and their combination can yield stronger constraints on δ₍CP₎. In particular, the differing energy ranges, baselines, and matter effects provide sensitivity that is not fully shared between the two methods. Realizing this potential will require further, but feasible, reductions in theoretical uncertainties. If achieved, this framework would provide an independent and robust probe as the next generation of neutrino experiments comes online to search for signals of CP violation.