Constraints on Oscillation Parameters from ν_e Appearance and ν_μ Disappearance in NOvA

Results are reported from an improved measurement of ν_μ→ν_e transitions by the NOvA experiment. Using an exposure equivalent to 6.05×10^(20) protons on target, 33 ν_e candidates are observed with a background of 8.2±0.8 (syst.). Combined with the latest NOvA ν_μ disappearance data and external constraints from reactor experiments on sin^2 2θ_(13), the hypothesis of inverted mass hierarchy with θ_(23) in the lower octant is disfavored at greater than 93% C.L. for all values of δ_(CP)

Search for active-sterile neutrino mixing using neutral-current interactions in NOvA

We report results from the first search for sterile neutrinos mixing with active neutrinos through a reduction in the rate of neutral-current interactions over a baseline of 810 km between the NOvA detectors. Analyzing a 14-kton detector equivalent exposure of 6.05×10^(20) protons-on-target in the NuMI beam at Fermilab, we observe 95 neutral-current candidates at the Far Detector compared with 83.5 ± 9.7(stat) ± 9.4(syst) events predicted assuming mixing only occurs between active neutrino species. No evidence for ν_μ→ν_s transitions is found. Interpreting these results within a 3+1 model, we place constraints on the mixing angles θ_(24) < 20.8° and θ_(34_ < 31.2° at the 90% C.L. for 0.05  eV^2 ≤ Δm^2_(41) ≤ 0.5  eV2, the range of mass splittings that produce no significant oscillations over the Near Detector baseline

New constraints on oscillation parameters from ν_e appearance and ν_μ disappearance in the NOvA experiment

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) = 2.44×10^(-3)  eV^2/c^4, sin^2 θ_(23) = 0.56, and δ_(CP) = 1.21π. The 68.3% confidence intervals in the normal mass hierarchy are Δm^2_(32) ∈ [2.37,2.52] × 10^(-3)  eV^2/c^4, sin^2 θ_(23) ∈ [0.43,0.51] ∪ [0.52,0.60], and δ_(CP) ∈ [0,0.12π] ∪ [0.91π,2π]. The inverted mass hierarchy is disfavored at the 95% confidence level for all choices of the other oscillation parameters

Measurement of the Neutrino Mixing Angle θ_(23) in NOvA

This Letter reports new results on muon neutrino disappearance from NOvA, using a 14 kton detector equivalent exposure of 6.05×10^(20) protons on target from the NuMI beam at the Fermi National Accelerator Laboratory. The measurement probes the muon-tau symmetry hypothesis that requires maximal θ_(23) mixing (θ_(23)=π/4). Assuming the normal mass hierarchy, we find Δm^2_(32)=(2.67±0.11)×10^(−3)  eV^2 and sin^2 θ_(23) at the two statistically degenerate values 0.404^(+0.030)_(−0.022) and 0.624^(+0.022)_(−0.030), both at the 68% confidence level. Our data disfavor the maximal mixing scenario with 2.6σ significance

Search for active-sterile neutrino mixing using neutral-current interactions in NOvA

We report results from the first search for sterile neutrinos mixing with active neutrinos through a reduction in the rate of neutral-current interactions over a baseline of 810 km between the NOvA detectors. Analyzing a 14-kton detector equivalent exposure of 6.05×10^(20) protons-on-target in the NuMI beam at Fermilab, we observe 95 neutral-current candidates at the Far Detector compared with 83.5 ± 9.7(stat) ± 9.4(syst) events predicted assuming mixing only occurs between active neutrino species. No evidence for ν_μ→ν_s transitions is found. Interpreting these results within a 3+1 model, we place constraints on the mixing angles θ_(24) < 20.8° and θ_(34_ < 31.2° at the 90% C.L. for 0.05  eV^2 ≤ Δm^2_(41) ≤ 0.5  eV2, the range of mass splittings that produce no significant oscillations over the Near Detector baseline

First Measurement of Coherent Elastic Neutrino-Nucleus Scattering on Argon

We report the first measurement of coherent elastic neutrino-nucleus scattering (\cevns) on argon using a liquid argon detector at the Oak Ridge National Laboratory Spallation Neutron Source. Two independent analyses prefer \cevns over the background-only null hypothesis with greater than $3\sigma$ significance. The measured cross section, averaged over the incident neutrino flux, is (2.2 $\pm$ 0.7) $\times$10$^{-39}$ cm$^2$ -- consistent with the standard model prediction. The neutron-number dependence of this result, together with that from our previous measurement on CsI, confirms the existence of the \cevns process and provides improved constraints on non-standard neutrino interactions.Comment: 8 pages, 5 figures with 2 pages, 6 figures supplementary material V3: fixes to figs 3,4 V4: fix typo in table 1, V5: replaced missing appendix, V6: fix Eq 1, new fig 3, V7 final version, updated with final revision

First measurement of muon-neutrino disappearance in NOvA

This paper reports the first measurement using the NOvA detectors of ν_μ disappearance in a ν_μ beam. The analysis uses a 14 kton-equivalent exposure of 2.74×10^(20) protons-on-target from the Fermilab NuMI beam. Assuming the normal neutrino mass hierarchy, we measure Δm^2_(32) =(2.52^(+0.20)_(−0.18))×10^(−3) eV^2 and sin^2 θ_(23) in the range 0.38–0.65, both at the 68% confidence level, with two statistically degenerate best-fit points at sin^2 θ_(23) =0.43 and 0.60. Results for the inverted mass hierarchy are also presented

COHERENT Collaboration data release from the measurements of CsI[Na] response to nuclear recoils

Description of the data release 10.13139/OLCF/1969085 (https://doi.ccs.ornl.gov/ui/doi/426) from the measurements of the CsI[Na] response to low energy nuclear recoils by the COHERENT collaboration. The release corresponds to the results published in "D. Akimov et al 2022 JINST 17 P10034". We share the data in the form of raw ADC waveforms, provide benchmark values, and share plots to enhance the transparency and reproducibility of our results. This document describes the contents of the data release as well as guidance on the use of the data

Monitoring the SNS basement neutron background with the MARS detector

We present the analysis and results of the first dataset collected with the MARS neutron detector deployed at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) for the purpose of monitoring and characterizing the beam-related neutron (BRN) background for the COHERENT collaboration. MARS was positioned next to the COH-CsI coherent elastic neutrino-nucleus scattering detector in the SNS basement corridor. This is the basement location of closest proximity to the SNS target and thus, of highest neutrino flux, but it is also well shielded from the BRN flux by infill concrete and gravel. These data show the detector registered roughly one BRN per day. Using MARS' measured detection efficiency, the incoming BRN flux is estimated to be $1.20~\pm~0.56~\text{neutrons}/\text{m}^2/\text{MWh}$ for neutron energies above $\sim3.5$~MeV and up to a few tens of MeV. We compare our results with previous BRN measurements in the SNS basement corridor reported by other neutron detectors.Comment: Submitted to JINS