Improved measurement of neutrino oscillation parameters by the NOvA experiment

We present new ν_μ→ν_e , ν_μ→ν_μ , ν_{¯ μ}→ν_{¯ e} , and ν_{¯ μ}→ν_{¯ μ} 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 ν_e, ν_μ, ν_¯e, and ν_¯μ 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 θ₂₃ mixing angle, with Δ m₃₂² =(2.41 ±0.07 )×10^-3 eV² and sin²θ₂₃ =0.5 7_-0.04^+0.03. The data disfavor combinations of oscillation parameters that give rise to a large asymmetry in the rates of ν_e and ν_¯e appearance. This includes values of the charge parity symmetry (CP) violating phase in the vicinity of δ_CP=π /2 which are excluded by >3 σ for the inverted mass ordering, and values around δ_CP=3 π /2 in the normal ordering which are disfavored at 2 σ confidence.