arXiv subjects

J. P. Davies

Publications and source records attributed to J. P. Davies.

7 recordsLinked to original sources

arXiv2017

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$\times$10$^{20}$ protons-on-target in the NuMI beam at Fermilab, we observe 95 neutral-current candidates at the Far Detector compared with $83.5 \pm 9.7 \mbox{(stat.)} \pm 9.4 \mbox{(syst.)}$ events predicted assuming mixing only occurs between active neutrino species. No evidence for $ν_μ \rightarrow ν_{s}$ transitions is found. Interpreting these results within a 3+1 model, we place constraints on the mixing angles $θ_{24}<20.8^{\circ}$ and $θ_{34}<31.2^{\circ}$ at the 90% C.L. for $0.05~eV^2\leq Δm^2_{41}\leq 0.5~eV^2$, the range of mass splittings that produce no significant oscillations over the Near Detector baseline.

hep-ex↗

arXiv2017

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

Results are reported from an improved measurement of $ν_μ\rightarrow ν_e$ transitions by the NOvA experiment. Using an exposure equivalent to $6.05\times10^{20}$ protons-on-target 33 $ν_e$ candidates were observed with a background of $8.2\pm0.8$ (syst.). Combined with the latest NOvA $ν_μ$ disappearance data and external constraints from reactor experiments on $\sin^22θ_{13}$, 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 $δ_{CP}$.

hep-ex↗

arXiv2017

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 $6.05\times10^{20}$ protons-on-target from the NuMI beam at the Fermi National Accelerator Laboratory. The measurement probes the muon-tau symmetry hypothesis that requires maximal mixing ($θ_{23} = π/4$). Assuming the normal mass hierarchy, we find $Δm^2 = (2.67 \pm 0.11)\times 10^{-3}$ 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 2.6 $σ$ significance.

hep-ex↗

arXiv2017

Constraints on the Ultra-High Energy Neutrino Flux from Gamma-Ray Bursts from a Prototype Station of the Askaryan Radio Array

We report on a search for ultra-high-energy (UHE) neutrinos from gamma-ray bursts (GRBs) in the data set collected by the Testbed station of the Askaryan Radio Array (ARA) in 2011 and 2012. From 57 selected GRBs, we observed no events that survive our cuts, which is consistent with 0.12 expected background events. Using NeuCosmA as a numerical GRB reference emission model, we estimate upper limits on the prompt UHE GRB neutrino fluence and quasi-diffuse flux from $10^{7}$ to $10^{10}$ GeV. This is the first limit on the prompt UHE GRB neutrino quasi-diffuse flux above $10^{7}$ GeV.

astro-ph.HE↗

arXiv2016

First measurement of electron neutrino appearance in NOvA

We report results from the first search for $ν_μ\toν_e$ transitions by the NOvA experiment. In an exposure equivalent to $2.74\times10^{20}$ protons-on-target in the upgraded NuMI beam at Fermilab, we observe 6 events in the Far Detector, compared to a background expectation of $0.99\pm0.11$ (syst.) events based on the Near Detector measurement. A secondary analysis observes 11 events with a background of $1.07\pm0.14$ (syst.). The $3.3σ$ excess of events observed in the primary analysis disfavors $0.1π< δ_{CP} < 0.5π$ in the inverted mass hierarchy at the 90% C.L.

hep-ex↗

arXiv2016

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 $2.74 \times 10^{20}$ protons-on-target from the Fermilab NuMI beam. Assuming the normal neutrino mass hierarchy, we measure $Δm^{2}_{32}=(2.52^{+0.20}_{-0.18})\times 10^{-3}$ eV$^{2}$ and $\sin^2θ_{23}$ in the range 0.38-0.65, both at the 68% confidence level, with two statistically-degenerate best fit points at $\sin^2θ_{23} = $ 0.43 and 0.60. Results for the inverted mass hierarchy are also presented.

hep-ex↗

arXiv2015

First Constraints on the Ultra-High Energy Neutrino Flux from a Prototype Station of the Askaryan Radio Array

The Askaryan Radio Array (ARA) is an ultra-high energy ($>10^{17}$ eV) cosmic neutrino detector in phased construction near the South Pole. ARA searches for radio Cherenkov emission from particle cascades induced by neutrino interactions in the ice using radio frequency antennas ($\sim150-800$ MHz) deployed at a design depth of 200 m in the Antarctic ice. A prototype ARA Testbed station was deployed at $\sim30$ m depth in the 2010-2011 season and the first three full ARA stations were deployed in the 2011-2012 and 2012-2013 seasons. We present the first neutrino search with ARA using data taken in 2011 and 2012 with the ARA Testbed and the resulting constraints on the neutrino flux from $10^{17}-10^{21}$ eV.

astro-ph.HE↗