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

TL;DR

This paper investigates the potential for CP-violating non-standard neutrino interactions using recent long-baseline data from NOvA and T2K, suggesting a possible new complex phase near maximal CP violation.

Contribution

It introduces a simple analytical approximation for NSI parameters and combines recent experimental data to hint at CP-violating NSI, comparing results with other constraints.

Findings

Hints of CP-violating NSI with a complex phase near 3π/2

Estimated NSI parameters around 0.2 in magnitude

Comparison with IceCube and COHERENT constraints

Abstract

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: $\phi_{e\mu}$ or $\phi_{e\tau}\approx3\pi/2$ with $|\epsilon_{e\mu}|$ or $|\epsilon_{e\tau}|\sim0.2$. We then compare the results from long-baseline data to constraints from IceCube and COHERENT.