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