The nature of the neutrino mass ordering and whether neutrino oscillations violate CP symmetry remain among several open questions surrounding PMNS mixing. At present no single experiment has the ability to resolve these issues. Atmospheric neutrino data at Super-Kamiokande (SK) and accelerator neutrino data from T2K, however, offer complementary sensitivity to these puzzles. As both neutrino sources are observed at the same detector, SK, there is a clear benefit to analyzing the data sets together. Here the first such combined analysis is performed, which utilizes unified uncertainty models of both neutrino interactions and the detector response.
Combined constraints on open questions in the PMNS paradigm are presented, using 3244.4 days of SK atmospheric neutrino data and beam neutrino data corresponding to $3.6\times 10^{21}$ protons-on-target from T2K’s first 10 run periods.
The analysis provides a marginal rejection of CP conservation and the inverted mass ordering hypotheses, with significance levels of 1.9$\sigma$ and 1.2$\sigma$ respectively.