An enhanced sample of low-energy electron neutrinos for improved NOvA mass ordering sensitivity

NOvA continues as a leading long-baseline neutrino experiment thanks to Fermilab's powerful 900 kW NuMI beam. A near detector at Fermilab samples the un-oscillated beam, while the far detector 810 km downstream, measures the oscillated spectrum. The long-baseline oscillation analysis probes the neutrino mass ordering, CP violation in the lepton sector, and the octant of the neutrino mixing angle θ₂₃. Sensitivity to the mass ordering is driven by our ability to measure the asymmetry between electron neutrino and antineutrino appearance rates, which varies as a function of neutrino energy. Positioning both detectors slightly off-axis produces a narrowband energy spectrum, peaked at 2 GeV that, coupled with a long baseline, gives NOvA good mass ordering sensitivity. Previous results were constrained by efficiency to 1-4.5 GeV. With the true mass ordering yielding the largest difference in this asymmetry below 1 GeV, we introduce a new classifier to reclaim precious 0.5-1.5 GeV events into the analysis, improving our mass ordering sensitivity. We present details of this new low-energy sample and expected sensitivity improvements.