Search for $CP$-Violating Neutrino Nonstandard Interactions with the NOvA Experiment

Abstract

This Letter reports a search for charge-parity ($CP$) symmetry violating nonstandard interactions (NSI) of neutrinos with matter using the NOvA Experiment, and examines their effects on the determination of the standard oscillation parameters. Data from $\hat{I}{½}_{\hat{I}}¼(\bar{\hat{I}}{½}_{\hat{I}}¼)\to \hat{I}{½}_{\hat{I}}¼(\bar{\hat{I}}{½}_{\hat{I}}¼)$ and $\hat{I}{½}_{\hat{I}}¼(\bar{\hat{I}}{½}_{\hat{I}}¼)\to \hat{I}{½}_e(\bar{\hat{I}}{½}_e)$ oscillation channels are used to measure the effect of the NSI parameters ${\epsilon }_{e\hat{I}¼}$ and ${\epsilon }_{e\ddot{I}„}$. With 90% CL the magnitudes of the NSI couplings are constrained to be $|{\epsilon }_{e\hat{I}¼}|\lesssim 0.3$ and $|{\epsilon }_{e\ddot{I}„}|\lesssim 0.4$. A degeneracy at $|{\epsilon }_{e\ddot{I}„}|\approx 1.8$ is reported, and we observe that the presence of NSI limits sensitivity to the standard $CP$ phase $\hat{I}{´}_{\text{CP}}$.