An Improved Measurement of Neutrino Oscillation Parameters by the NOvA Experiment

Abstract

We present new $\hat{I}{½}_{\hat{I}}¼\to \hat{I}{½}_e$, $\hat{I}{½}_{\hat{I}}¼\to \hat{I}{½}_{\hat{I}}¼$, $\overline{\hat{I}}{½}_{\hat{I}}¼\to \overline{\hat{I}}{½}_e$, and $\overline{\hat{I}}{½}_{\hat{I}}¼\to \overline{\hat{I}}{½}_{\hat{I}}¼$ oscillation measurements by the NOvA experiment, with a 50% increase in neutrino-mode beam exposure over the previously reported results. The additional data, combined with previously published neutrino and antineutrino data, are all analyzed using improved techniques and simulations. A joint fit to the $\hat{I}{½}_e$, $\hat{I}{½}_{\hat{I}}¼$, $\overline{\hat{I}}{½}_e$, and $\overline{\hat{I}}{½}_{\hat{I}}¼$ candidate samples within the 3-flavor neutrino oscillation framework continues to yield a best-fit point in the normal mass ordering and the upper octant of the $\hat{I}{¸}_{23}$ mixing angle, with $\hat{I}”m_{32}^2=(2.41\pm 0.07)\times 10^{-3}$ eV${}^2$ and ${\sin }^2\hat{I}{¸}_{23}=0.57_{-0.04}^{+0.03}$. The data disfavor combinations of oscillation parameters that give rise to a large asymmetry in the rates of $\hat{I}{½}_e$ and $\overline{\hat{I}}{½}_e$ appearance. This includes values of the CP-violating phase in the vicinity of $\hat{I}{´}_{\text{CP}}=\ddot{I}€/2$ which are excluded by $>3\ddot{I}ƒ$ for the inverted mass ordering, and values around $\hat{I}{´}_{\text{CP}}=3\ddot{I}€/2$ in the normal ordering which are disfavored at 2$\ddot{I}ƒ$ confidence.

11 pages, 6 figures. Supplementary material attached (7 figures)