Improved measurement of neutrino oscillation parameters by the NOvA experiment

Abstract

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 θ 23 mixing angle, with Δ m 2 32 = ( 2.41 ± 0.07 ) × 10 − 3

eV 2 and sin 2 θ 23 = 0.5 7 + 0.03 − 0.04 . 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.