<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>C</mml:mi><mml:mi>P</mml:mi></mml:math>-Violating Neutrino Nonstandard Interactions in Long-Baseline-Accelerator Data
Peter B. Denton, Julia Gehrlein, R. Pestes
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 nonstandard 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: ${\ensuremath{\phi}}_{e\ensuremath{\mu}}$ or ${\ensuremath{\phi}}_{e\ensuremath{\tau}}\ensuremath{\approx}3\ensuremath{\pi}/2$ with $|{\ensuremath{\epsilon}}_{e\ensuremath{\mu}}|$ or $|{\ensuremath{\epsilon}}_{e\ensuremath{\tau}}|\ensuremath{\sim}0.2$. We then compare the results from long-baseline data to constraints from IceCube and COHERENT.