The NOvA experiment has seen a 4.4σ signal ofν e appearance in a 2 GeVν μ beam at a distance of 810 km. Using 12.33 × 10 20 protons on target delivered to the Fermilab NuMI neutrino beamline, the experiment recorded 27ν μ →ν e candidates with a background of 10.3 and 102ν μ →ν μ candidates. This new antineutrino data are combined with neutrino data to measure the parameters jΔm 2 32 j ¼ 2.48 þ0.11 −0.06 × 10 −3 eV 2 =c 4 and sin 2 θ 23 in the ranges from (0.53-0.60) and (0.45-0.48) in the normal neutrino mass hierarchy. The data exclude most values near δ CP ¼ π=2 for the inverted mass hierarchy by more than 3σ and favor the normal neutrino mass hierarchy by 1.9σ and θ 23 values in the upper octant by 1.6σ.
We present updated results from the NOvA experiment for ν μ → ν μ and ν μ → ν e oscillations from an exposure of 8.85 × 10 20 protons on target, which represents an increase of 46% compared to our previous publication. The results utilize significant improvements in both the simulations and analysis of the data. A joint fit to the data for ν μ disappearance and ν e appearance gives the best-fit point as normal mass hierarchy, Δm 2 32 ¼ 2.44 × 10 −3 eV 2 =c 4 , sin 2 θ 23 ¼ 0.56, and δ CP ¼ 1.21π. The 68.3% confidence intervals in the normal mass hierarchy are Δm 2 32 ∈ ½2.37; 2.52 × 10 −3 eV 2 =c 4 , sin 2 θ 23 ∈ ½0.43; 0.51 ∪ ½0.52; 0.60, and δ CP ∈ ½0; 0.12π ∪ ½0.91π; 2π. The inverted mass hierarchy is disfavored at the 95% confidence level for all choices of the other oscillation parameters.
The NOvA long-baseline neutrino experiment uses a pair of large, segmented, liquid-scintillator calorimeters to study neutrino oscillations, using GeV-scale neutrinos from the Fermilab NuMI beam. These detectors are also sensitive to the flux of neutrinos which are emitted during a core-collapse supernova through inverse beta decay interactions on carbon at energies of O(10 MeV). This signature provides a means to study the dominant mode of energy release for a core-collapse supernova occurring in our galaxy. We describe the datadriven software trigger system developed and employed by the NOvA experiment to identify and record neutrino data from nearby galactic supernovae. This technique has been used by NOvA to self-trigger on potential core-collapse supernovae in our galaxy, with an estimated sensitivity reaching out to 10 kpc distance while achieving a detection efficiency of 23% to 49% for supernovae from progenitor stars with masses of 9.6 M to 27 M , respectively.
The two-detector design of the NOvA neutrino oscillation experiment, in which two functionally identical detectors are exposed to an intense neutrino beam, aids in canceling leading order effects of cross-section uncertainties. However, limited knowledge of neutrino interaction cross sections still gives rise to some of the largest systematic uncertainties in current oscillation measurements. We show contemporary models of neutrino interactions to be discrepant with data from NOvA, consistent with discrepancies seen in other experiments. Adjustments to neutrino interaction models in GENIE are presented, creating an effective model that improves agreement with our data. We also describe systematic uncertainties on these models, including uncertainties on multi-nucleon interactions from a newly developed procedure using NOvA near detector data.
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