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

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 ${\nu }_{\mu }({\bar{\nu }}_{\mu })\to {\nu }_{\mu }({\bar{\nu }}_{\mu })$ and ${\nu }_{\mu }({\bar{\nu }}_{\mu })\to {\nu }_e({\bar{\nu }}_e)$ oscillation channels are used to measure the effect of the NSI parameters ${\epsilon }_{e\mu }$ and ${\epsilon }_{e\tau }$. With 90% CL the magnitudes of the NSI couplings are constrained to be $\mathrm{\mid }{\epsilon }_{e\mu }\mathrm{\mid }\lesssim 0.3$ and $\mathrm{\mid }{\epsilon }_{e\tau }\mathrm{\mid }\lesssim 0.4$. A degeneracy at $\mathrm{\mid }{\epsilon }_{e\tau }\mathrm{\mid }\approx 1.8$ is reported, and we observe that the presence of NSI limits sensitivity to the standard $CP$ phase ${\delta }_{\text{CP}}$.