CP-Violating Neutrino Non-Standard Interactions in Long-Baseline-Accelerator Data

Neutrino oscillations in matter provide a unique probe of new physics. Leveraging the advent of neutrino appearance data from NOvA and T2K in recent years, we investigate the presence of CP-violating neutrino non-standard interactions in the oscillation data. We first show how to very simply approximate the expected NSI parameters to resolve differences between two long-baseline appearance experiments analytically. Then, by combining recent NOvA and T2K data, we find a tantalizing hint of CP-violating NSI preferring a new complex phase that is close to maximal: $phi_{emu}$ or $phi_{etau}approx3pi/2$ with $|epsilon_{emu}|$ or $|epsilon_{etau}|sim0.2$. We then compare the results from long-baseline data to constraints from IceCube and COHERENT.