Precision Measurement of Neutrino Oscillation Parameters with 10 Years of Data from the NOvA Experiment

This Letter reports measurements of muon-neutrino disappearance and electron-neutrino appearance and the corresponding antineutrino processes between the two NOvA detectors in the NuMI neutrino beam. These measurements use a dataset with double the neutrino mode beam exposure that was previously analyzed, along with improved simulation and analysis techniques. A joint fit to these samples in the three-flavor paradigm results in the most precise single-experiment constraint on the atmospheric neutrino mass splitting, Δm_{32}^{2}=2.431_{-0.034}^{+0.036}(-2.479_{-0.036}^{+0.036})×10^{-3}  eV^{2} if the mass ordering is normal (inverted). In both orderings, a region close to maximal mixing with sin^{2}θ_{23}=0.55_{-0.06}^{+0.02} is preferred. The NOvA data show a mild preference for the normal mass ordering with a Bayes factor of 2.4 (corresponding to 70% of the posterior probability), indicating that the normal ordering is 2.4 times more probable than the inverted ordering. When incorporating a 2D Δm_{32}^{2}-sin^{2}2θ_{13} constraint based on Daya Bay data, this preference strengthens to a Bayes factor of 6.6 (87%).